perpendicular recording
fig. 1 illustrates an example perpendicular magnetic recording system 100. the perpendicular magnetic recording system 100 includes a read / write head 102, which generates a magnetic field perpendicular to a perpendicular magnetic recording stack 104 .
a book on perpendicular recording is recently published by kluwer academic press: s. khizroev and d. litvinov “perpendicular magnetic recording”, 2004
perpendicular recording: a new approach to writing on magnetic media that aligns bits vertically, perpendicular ...
on next page we will explain how perpendicular recording works and we will compare it to longitudinal recording .
reproduced voltage versus linear bit density characteristics for perpendicular magnetic recording with various recording layer thickness, δ .
fig. 1 is a schematic representation of a perpendicular magnetic recording system with a prior art patterned perpendicular medium .
perpendicular recording is a method of recording data to a hard disk drive (hdd). perpendicular recording aligns data bits vertically — perpendicular to the disk, which allows for additional room on a disk to pack more data, thus, enabling higher recording densities. contrast with longitudinal recording .
perpendicular magnetic recording systems, such as systems including a perpendicular recording head and a perpendicular magnetic recording stack with a coupled granular / continuous (cgc) structure having a dual continuous layer, can exhibit ultra high density recording capability resulting in an increased storage capacity .
the above analysis of both the tilted perpendicular recording and the perpendicular recording based on micromagnetic simulations suggests that, the tilted perpendicular recording system can significantly increase the medium thermal stability as compared to both the longitudinal and the perpendicular recording. for example, a possible gain in stability from 50% to about 100% may be achieved over the perpendicular recording. a feasible smaller transition parameter and a larger snr can be achieved in the tilted perpendicular recording than the perpendicular recording. an almost instantaneous switching in the tilted medium is obtained in the tilted perpendicular recording. this switching may be used to achieve a data rate above 2 ghz. the tilted recording system has much less fringing problem as compared to both the longitudinal and the perpendicular recording .
the perpendicular recording system is suitable for high density recording because of the strong magnetic coupling between neighboring magnetic bits .
the invention is also a magnetic recording disk drive that incorporates the above - described patterned perpendicular magnetic recording disk .
fig. 2 illustrates an example perpendicular magnetic recording stack having a dual continuous layer .
4. the perpendicular magnetic recording medium of claim 1, wherein the interlayer comprises ru .
information may be stored on a perpendicular magnetic recording stack. such information may be written to and / or read from the perpendicular magnetic recording stack using a read / write head .
considering the evolution to the novel perpendicular magnetic recording, i particularly examined the complementary relation to conventional longitudinal recording, which is the complementary nature between the two recording modes .
perpendicular (solid lines) and in - plane (broken lines) hysteresis curves of co - cr perpendicular recording media with various cr contents .
year - by - year trend of the number of papers related to perpendicular magnetic recording for journals of the ieee magnetics society, and for the perpendicular magnetic recording conference (pmrc) .
the present tapered write head designs and the tilted perpendicular recording media are in part based on recognition of certain technical limitations of the in longitudinal and perpendicular recording systems with conventional write heads .
the following sections first describe examples of tapered single pole write heads and titled perpendicular recording media. next, certain limitations of longitudinal and perpendicular recording systems with conventional write heads are discussed to illustrate some of the advantages and benefits of the combinations of the tapered single pole write heads and titled perpendicular recording media. in addition, various designs of tapered single pole write heads are described. such tapered single pole write heads may be used with various perpendicular recoding media including the tilted perpendicular recording media as illustrated in the specific examples in this application and non - tilted perpendicular recording media such as various perpendicular recording media .
flux flow in a double - layered perpendicular magnetic recording medium. horseshoe - shaped bits are formed with the perpendicular and in - plane anisotropy films .
3. the perpendicular magnetic recording medium of claim 1, wherein the magnetic layer comprises cocrpt .
however, as the perpendicular recording components were developed, numerous disadvantages were discovered. here is a list of some of the disadvantages of the perpendicular system :
in a perpendicular recording media, magnetization is formed easily in a direction perpendicular to the surface of a magnetic medium such that bits stand up and be perpendicular to surface, resulting from perpendicular anisotropy in the magnetic recording layer. on the other hand, in a longitudinal recording media, magnetization is formed in a direction in a plane parallel to the surface of the magnetic recording layer, resulting from longitudinal anisotropy in the magnetic recording layer .
fig. 5 shows simulation results of the a m - h loop for typical perpendicular recording media .
due to at lest the above reasons, the thermal stability is a problematic in the perpendicular recording .
5. the perpendicular magnetic recording medium of claim 1, wherein the interlayer comprises and metal oxide .
fig. 3 illustrates example operations for manufacturing a perpendicular magnetic recording stack having a dual continuous layer .
the long argument between longitudinal and perpendicular recording was settled at last. it can be said that it was a moment at which the true value of perpendicular magnetic recording was recognized for the first time widely and to a great degree. for this very reason, the strong impetus for development of perpendicular recording resumed .
perpendicular recording is the hard drive industry' s answer to the superparamagnetic effect. as its name implies, perpendicular recording aligns bits vertically—perpendicular to the disk surface. this recording method allows drive manufacturers to increase a disc' s areal density without shrinking bits to a point where they become vulnerable to the superparamagnetic effect .
fig. 2 illustrates an example perpendicular magnetic recording stack 200 having a dual continuous layer. in one implementation, the perpendicular recording stack 200 includes a substrate 202, an underlayer 204, a magnetic granular recording layer 214, a dual continuous layer 224, and an overcoat 230. however, the perpendicular magnetic recording stack 200 may have more or less layers .
perpendicular recording technology achieves 1. 8 - inch drive that holds the industry largest 80 - gigabytes of information
the structure of perpendicular pole head with soft underlayer provides an immediate advantage of perpendicular recording over longitudinal: the magnitude of the recording field in this configuration is increased by approximately a factor of 2 over longitudinal medium .
fig. 3 illustrates example operations 300 for manufacturing a perpendicular magnetic recording stack having a dual continuous layer .
this invention relates generally to patterned perpendicular magnetic recording media, such as disks for use in magnetic recording hard disk drives, and more particularly to patterned disks with data islands having improved magnetic recording properties .
one advantage for the perpendicular recording is that the medium thickness can be larger than that in the perpendicular recording. however, as the recording densities increase, the medium thickness of the perpendicular recording is also limited. large thickness medium can cause the write field to decrease. this decrease is undesirable because it limits the h k of the medium that can be written on .
, it is readily apparent that demagnetization caused by random thermal fluctuation is very much suppressed in perpendicular magnetic recording .
read - back resolution of perpendicular recording medium is lower compared with longitudinal medium due to the presence of sul .
2. longitudinal recording system (conventional) recorded magnets repulse and weaken each other in longitudinal recording .
in the storage device industry to commercialize perpendicular magnetic recording, and the company has applied the technology to hdd that achieve unsurpassed recording density and high operating reliability. this success rests on development of a new magnetic disk structured to support perpendicular recording, a new high performance perpendicular magnetic head, and disk and head integration technology that maximizes their combined performance .
in the longitudinal recording, the medium coercivity h c is approximately in the range of between 0. 5 hk and 0. 6 h k due to the perpendicular component of the write field at the tips and boundaries from the write poles. in the perpendicular recording, the medium h k is in the perpendicular direction. the largest component of write field from single pole head with sul is also in the perpendicular direction, parallel to the medium anisotropy. as can be seen in fig. 4, for same h k media, a larger write field is required in the perpendicular recording as compared to the longitudinal recording. by doing so, the values of h k for perpendicular media that can be written in the perpendicular recording are not much higher than the longitudinal recording .
the figure shows how recorded magnetization changes according to the thermal fluctuation as the recording density is increased. with longitudinal recording, recording bits become increasingly unstable as the recording density is increased, in contrast, in perpendicular magnetic recording, the recorded magnetization becomes more stable at high densities. this is a typical difference derived from inherent essential natures of the two recording modes. as a consequence, it can be concluded that perpendicular recording is fundamentally appropriate for high - density recording. in perpendicular magnetic recording, the head and disk strongly interact with each other, which brings stability against ambient circumstance such as temperature and air pressure, which in turn affects spacing of the head and medium .
after these experiments, i once more inferred that two possibilities would become particularly important in the future of perpendicular magnetic recording .
this application provides, among others, perpendicular magnetic recording systems that use tapered single pole write heads. suitable magnetic recording media include tilted perpendicular recording media where the anisotropy directions of a layer of magnetic grains for recording are tilted from the direction perpendicular to the layer, and non - tilted perpendicular recording media where the anisotropy directions of a layer of magnetic grains for recording are substantially perpendicular to the layer without tilting. the tapering of the single pole write heads may be designed to produce large down - track field strength and field gradient to produce sharp transitions in writing data and to produce large off - track field gradient to avoid erasure of neighboring tracks in high density media .
the recording medium is characterized by the recording layer thickness, distance between recording layer and the soft underlayer and the thickness of the soft under - layer. each of the head and media parameters influences the recording process .
prototyping of a hard disk drive using perpendicular magnetic recording (52. 5 gb / in 2) and its recording bit image on the disk, by hitachi ltd. 15 )
fig. 7b shows simulation results of the medium switching field distribution along the center track for the perpendicular and longitudinal recording media .
what is needed is a patterned perpendicular magnetic recording medium that has a narrow sfd and is less susceptible to adjacent track overwrite .
during that work, it became clear to me that the increase of recording density was most important for research on magnetic recording. the invention of metal tape described above and the establishment of the theory of high - density magnetic recording were both achievements along that path of development. moreover, i had noticed by 1975 that magnetization perpendicular to the plane of the recording medium was an extremely effective means to improve the recording density. 3), 4) these speculations and four discoveries are shown as major milestones in the early research on perpendicular magnetic recording that guided the beginning of perpendicular magnetic recording, as the following .
fig. 9 shows simulation results of the switching field distribution with respect to the write field angle for the titled perpendicular media and conventional perpendicular media .
fig. 10 shows simulation results of the switching speed as a function of the damping constant for both the titled perpendicular media and conventional perpendicular media .
magnetic recording traditionally uses a longitudinal recording method where a recording medium is configured to have its anisotropy easy axes along the longitudinal directions within the magnetic recording medium plane. the storage density based on this method is known to be limited due to the thermal instability of the magnetic grains. an improved method based on a perpendicular recording configuration has been developed to mitigate some technical limitations in the longitudinal recording devices, e. g. , to achieve better thermal stability than the longitudinal recording. typically, a perpendicular recording configuration uses media with their medium anisotropy easy axes perpendicular to the medium plane and a single pole head with a soft magnetic under layer to enhance the write field. another magnetic recording technique called “tilted longitudinal recording” has also been developed to use an inductive head with a tilted medium .
fig. 7a shows simulation results of the spatial profiles of the perpendicular field, filed angle, and the medium coercivity relative to the field anisotropy along the center track of the perpendicular and longitudinal recording media .
in one embodiment, the invention generally provides a perpendicular recording medium comprising a magnetic layer, wherein the magnetic layer exhibits improved corrosion resistance while maintaining the magnetic properties suitable for high density perpendicular recording. one embodiment provides a perpendicular recording medium comprising a magnetic layer, wherein the magnetic layer comprises cobalt (co), platinum (pt), and at least one of molybdenum (mo) and chromium (cr), the magnetic layer having perpendicular magnetic anisotropy. another embodiment provides a granular perpendicular recording medium comprising a granular magnetic layer, wherein the magnetic layer comprises co, pt, and at least one of mo and cr, the granular magnetic layer having perpendicular magnetic anisotropy .
comparison of longitudinal and perpendicular recording can be found in: h. n. bertram and m. williams “snr and density limit estimates: a comparison of longitudinal and perpendicular recording” – ieee trans. magnetics, vol. 36, pp. 4 - 9, 2000
fig. 1 illustrates an example of a single pole write head for writing on a titled or non - titled perpendicular recording medium .
can be derived with respect to the magnetic head, recording medium, signals, and recording method. this complementarity relation
this comparison of normalized roll - off curves is not completely honest – it is difficult to achieve a longitudinal pw50 as narrow, as the ones which be obtained with perpendicular recording. assuming the same pulse width can be achieved, the perpendicular recording has intrinsically lower resolution .
magnetic flux distribution of a perpendicular head in an enlarged model experiment. this photograph appeared on the cover of a magazine, nikkei electronics, of august 7, 1978, 5) which reported perpendicular magnetic recording .
fig. 4 shows simulation results of the angles of media coercivity fields with respect to media anisotropy in both perpendicular and longitudinal recording systems .
2. the perpendicular magnetic recording medium of claim 1, wherein the magnetic layer comprises argon ions on a surface of the magnetic layer .
fig. 8 also shows that the nucleation field of the tilted medium, defined as the negative field with the first medium grain reversed, is also much larger (than that of the perpendicular medium. the absolute value of hn for tilted perpendicular media is smaller than that for the perpendicular media, the ratio of abs (hn / how) for tilted perpendicular recording media is much larger than that for conventional perpendicular recording media. based on the data in fig. 8, in the illustrated tilted perpendicular recording medium, this ratio is about (0. 4 / 0. 65) = 0. 61 while the ratio for the conventional perpendicular recording medium is about (0. 6 / 1. 35) = 0. 44. this implies less medium noise and larger thermal stability in both the high density and the low density recording .
the first data of recording magneto - motive force versus reproduced output characteristics of a double - layered perpendicular medium and a single - pole head in comparison to a single layer perpendicular medium (may 19, 1978) .
fig. 5 is a schematic of the write process on patterned perpendicular media .
is seagate' s barracuda 7200. 10 as good as it sounds? and what' s the deal with perpendicular recording technology, anyway ?
the storage capacity of a perpendicular magnetic recording stack may be improved by increasing the areal density of a magnetic granular recording layer. however, as the areal density of a magnetic granular recording layer increases, other performance factors may become more relevant, including without limitation the thermal stability of the magnetic granular recording layer, recording ease (i. e. , writability), and media noise .
. therefore, it is very structure - oriented. for the perpendicular magnetic recording, in contrast, because its resolution depends entirely on the playback head resolution, the smallest bit on the recording layer can be formed as small as the size of fine grains of the magnetic film. perpendicular magnetic recording can be said to be more material - oriented .
in perpendicular magnetic recording, because the bit magnetization is aligned in an anti - parallel way, the recording bits are mutually attracted with respect to the magnetic force, which allows them to be packed densely to produce a highly dense configuration. in similar fashion, because the head and medium are also mutually attractive, the writing head field distribution becomes steeper and more focused as the medium approaches the head. for that reason, a narrow track recording is readily realized. it can attain a high linear recording density and can simultaneously accommodate even a narrow track recording. therefore, the areal recording density is more easily increased using perpendicular recording than using longitudinal recording. 13 )
the answer is simple: nobody knows for sure. the history of perpendicular recording started many decades ago, almost simultaneously with longitudinal recording. many attempts have been made to develop a perpendicular recording system, however the industry was successfully introducing new generations of longitudinal components, achieving high areal density. the development of high density systems required complicated optimization of recording heads and media, consuming efforts of large groups of scientists and engineers. the few parts, which were produced never demonstrated any advantages over longitudinal recording components. the research in perpendicular recording was left to several university groups and was not considered to be worth much of attention .
in the above examples of the tilted perpendicular recording, tapered single pole write heads are used to produce large down - track field and field gradient and to generate a large off - track field gradient. in addition, the tapering effectively reduces the footprint of the write pole on the recording media and thus allows for higher data densities. these and other desirable properties of the tapered single pole write heads may be used to improve performance of other perpendicular recording media such as non - tilted perpendicular recording media where the anisotropy axes of the magnetic grains are substantially perpendicular to the media surface .
a single pole head with the sul and the tapered neck with a small throat height can achieve large perpendicular recording field with large field gradient. in the perpendicular recording, the medium coercivity decreases with the write field. the effective write field gradient is small. in the present tilted perpendicular recording, the recording system can be optimized with respect to the medium tilted angle so that the direction of the optimum recording field at the transition center can be close to 45° with respect to the perpendicular direction. therefore, close to the transition center where the largest perpendicular field gradient occurs, the medium coercivity increases with decreasing write field. under these conditions, a large effective field gradient is produced and thus the medium transition parameter can be reduced .
thermal stability of recording bits of a hard disk drive, indicating that the higher the density of perpendicular magnet recording, the less the decrease the stability becomes, thereby showing sufficient stability, by toshiba. 17 )
7. the perpendicular magnetic recording medium of claim 1, the magnetic layer comprising cobalt, platinum, and at least one of molybdenum and chromium .
. however, what i found is that another mode exists in which we can align magnets perpendicularly to the tape plane, as depicted in (b) of the figure. this is the ‘perpendicular mode’, or perpendicular magnetic recording .
the idea of perpendicular magnetic recording came to my mind first and foremost when i considered the possibility of using the perpendicular component of the magnetization directly for high - density magnetic recording because it always appeared in the pursuit of high - density recording, as described above. in the following, i will describe the early experiment that made me think of that idea (see
the majority of hard disk drives found on the market today use a recording technology called longitudinal, where bits are stored side by side on the magnetic surface. this recording technique has been used since the first hard disk drives. a new recording technology, called perpendicular, is being used on newer hard disk drives, allowing a higher recording density. in this tutorial we will explain you everything you need to know about perpendicular recording and how data is stored on the hard disk drive magnetic surface .
the breakthrough that transcended this areal density limitation was perpendicular magnetic recording. the dotted line in the figure marks the density trend of perpendicular magnetic recording. it extends the trend more than 100 gbit / inch 2 with a linear development, possibly entering into the terabit density domain. the fact that the trend of perpendicular recording shows a linear line throughout the entire period from the experimental age to the actual mass - production age proves that the combination of the principle and its associated devices to achieve high - density recording was correct .
s ince the first time
get perpendicular
got stuck in our heads, we' ve anxiously anticipated the arrival of perpendicular recording technology. the wait has been long, especially on the desktop, but perpendicular recording has finally arrived in seagate' s barracuda 7200. 10 hard drive. and it' s arrived in style. seagate has exploited the new recording technology to offer a drive with a monstrous 750 gb capacity—50% more than any other drive on the market .
lee, k. j. , et al. ,
recording physics of perpendicular recording with single layered medium and ring head ,
journal of applied physics, 91 (10): 8700 - 8702, may 2002 .
3. the magnetic recording head as in claim 1, wherein the tapered neck has a straight profile along tracks on the recording medium .
the shape of the perpendicular recording signal read - back also depends on the track width. the narrower the recorded track, the less is the field cancellation effect (fce) and the read - back waveform is closer to rectangular. this is easily understood from the fact that for perpendicular recording media both down - track and cross - track directions are equivalent (they are perpendicular to the medium magnetization direction) .
figs. 2a, 2 b, 3 a, and 3 b show two examples of tapered single pole write heads and an example of titled perpendicular recording media .
iwasaki, s. ,
perpendicular magnetic recording ,
ieee transactions on magnetics, mag - 16 (1): 71 - 76, jan. 1980 .
an example of a tilted perpendicular magnetic recording medium is also described to include a magnetic layer and a soft magnetic under layer beneath the magnetic layer. the magnetic layer includes magnetic grains with anisotropy easy axes tilted with respect to a perpendicular direction that is perpendicular to the magnetic layer. when combined with a tapered single pole write head, such a recording medium may provide better recording performance than other recording systems, such as improved thermal stability, a higher anisotropy field h k, smaller switching field distribution, reduced noise, and faster switching speed. high storage densities above 10 2 gbits / in 2, e. g. , at the level of tbits / in 2, can be obtained in such a tilted perpendicular recording system .
the medium 102 has a structure for perpendicular recording and may be implemented as a tilted perpendicular medium or a non - tilted perpendicular medium. the medium 102 may be a disk having multiple layers formed on a substrate. as one example, the medium may include a magnetic medium layer, a growth layer beneath the magnetic medium layer, and a soft under layer beneath the growth layer. as an example of the non - tilted perpendicular recording media, the magnetic medium layer may include magnetic grains that are grown along the perpendicular direction and have their anisotropy directions in the perpendicular direction. alternatively, the magnetic medium layer may include magnetic grains that are grown along the perpendicular direction but have their anisotropy directions tilted at a predetermined angle or angles with respect to the perpendicular direction. a tilted perpendicular medium may also be constructed to have at least one magnetic layer with perpendicular anisotropy between two magnetic exchange coupling or anti - ferromagnetic coupling layers. the magnetic interactions of these layers produce an effective tilted anisotropy of the multi - layer structure. two or more such multi - layer structures may be stacked .
perpendicular media grains are strongly oriented. this results in smaller medium noise and a sharper recorded transition. the high orientation of the perpendicular medium also improves side - track writing and edge noise .
fig. 8 shows simulation results of the remanent m - h loops for the titled perpendicular media and conventional perpendicular media where the cone angle distribution for the anisotropy axes is within 3 degrees .
the next important development was the perpendicular recording medium. a medium material was required for which the magnetic surface poles of n and s were retained on the surface plane, which is designated as a perpendicular anisotropy film. we found in 1975 that a thin film made of cobalt (co) and chromium (cr) alloy was the most promising perpendicular medium material. luckily enough, that material was available as a result of research work of magneto - optical recording, which was being conducted parallel in our laboratory at that time. this finding ultimately created the most effective means of accomplishing perpendicular magnetic recording .
figs. 7a - 7e are sectional views of a single discrete magnetic island on a patterned perpendicular magnetic recording medium for different implementations of the medium according to this invention .
6. the perpendicular magnetic recording medium of claim 1, wherein the magnetic layer comprises a co - containing magnetic material that forms less than 10 atomic percent coox in the co - containing magnetic material after exposure of the perpendicular magnetic recording medium to an environment having 80% relative humidity at 80 degree c. for at least four days .
magnetic recording hard disk drives with patterned magnetic recording media have been proposed to increase data density. in conventional continuous magnetic recording media, the magnetic recording layer is a continuous layer over the entire surface of the disk. in patterned media the magnetic recording layer on the disk is patterned into small isolated data islands arranged in concentric data tracks. patterned - media disks may be longitudinal magnetic recording disks, wherein the magnetization directions are parallel to or in the plane of the recording layer, or perpendicular magnetic recording disks, wherein the magnetization directions are perpendicular to or out - of - the - plane of the recording layer. perpendicular media will likely be the choice for patterned media because of the increased data density potential of perpendicular media. to produce magnetic isolation of the patterned data islands, the magnetic moment of the spaces between the islands are destroyed or substantially reduced to render these spaces essentially nonmagnetic. alternatively, the media may be fabricated so that that there is no magnetic material in the spaces between the islands. u. s. pat. no. 5, 820, 769 describes a type of patterned perpendicular media and its fabrication method .
magnetic recording techniques, devices, and systems under a tilted perpendicular recording configuration. an implementation of such a system may include a magnetic head having a single pole to produce a magnetic field along a perpendicular direction; and a storage medium having a top surface to be substantially perpendicular to the perpendicular direction and positioned to interact with the magnetic field, wherein the storage medium includes (1) a magnetic medium layer that has anisotropy easy axes tilted at a tilting angle with respect to the perpendicular direction, (2) a growth layer beneath the magnetic medium layer, and (3) a soft under layer beneath the growth layer .
therefore, the roll - off (amplitude versus recorded density) behavior of the perpendicular system is quite complicated with signal shape and amplitude depending on numerous factors, such as recording density, track width, sul thickness, distance to the sul etc. intrinsically larger amplitude of the perpendicular signal at lower densities rolls off faster at higher recording density. therefore, it is not clear how to estimate gains and losses of the perpendicular system read - back. also, it is very difficult to compare perpendicular read - back signal with longitudinal .
perpendicular prml channels were described in: m. madden. m. oberg, z. wu and r. he “read channel for perpendicular magnetic recording” – ieee trans. magnetics, vol. 30, pp. 241 - 246, 2004 r. cidecian, e. eleftheriou and t. mittelholzer “perpendicular and longitudinal recording: a signal processing and coding perpective” – ieee trans. magnetics, vol. 38, pp. 1698 - 1704, 2002
prior to the perpendicular method, the bits were written horizontally on the recording surface of the disk platter. (assistance with these illustrations courtesy of hitachi global storage technologies. )
a higher recording field is very advantageous for magnetic recording. not only does the cylindrical structure of perpendicular medium grains provide better thermal stability, the ability to overwrite high coercivity medium allows higher anisotropy and improves thermal stability even further. also, the higher coercivity medium has a smaller transition parameter and allows recording at higher linear density .
looking back at how the perpendicular anisotropy magnetic film was found, the major factors were the following .
shielded pole heads are becoming popular in perpendicular recording. the idea is to place a high permeability shield next to the recording pole. this shield “sucks” some of the head flux and improves the head gradient, while slightly reducing the deep gap field. the shielded head has an additional advantage – a larger horizontal magnetic field component helps to switch perpendicular media .
generally, lowering exchange coupling of perpendicular recording media causes their magnetic hysteresis loops to become more sheared, and correspondingly have a larger difference between coercive field (hc) and nucleation field (hn). there are many prior examples of this relationship between exchange coupling and hc - hn for cocr - based and reactive oxygen - based sputtered perpendicular recording media .
7. the magnetic recording head as in claim 1, wherein the single - pole magnetic write tip comprises a plurality of magnetic layers along the direction substantially perpendicular to the recording medium, wherein two adjacent magnetic layers have equilibrium magnetizations in substantially opposite directions .
in one implementation, the perpendicular magnetic recording stack 104 includes a substrate 106, one or more underlayers 108, one or more magnetic granular recording layers 110, and a dual continuous layer including a first continuous layer 112 and a second continuous layer 114 .
in america, at around 1982, several venture companies of perpendicular recording had been founded. in a similar fashion, from around 1985, american universities started supporting magnetic recording research centers one after another. i believe that happened because of the impact of our 144 committee on magnetic recording in japan society for the promotion of science (jsps), which was described above in section 3. subsequently, ibm proposed a new read head using the magneto - resistive (mr) effect, which produced a separate stream from perpendicular recording in the roadmap, however even during that time, our committee continued steadily with its activities to promote perpendicular recording; now we have had meetings more than 190 times .
hitachi will present these achievements at the 8th perpendicular magnetic recording conference (pmrc 2007), to be held 15th - 17th october 2007, at the tokyo international forum in japan .
as the technology progressed, it has become clear that the thermal stability gains are smaller than expected, but there are many other, less evident advantages of the perpendicular recording scheme .
the numerous theoretical predictions and experimental evaluations of the perpendicular recording potential are all over the place. the most optimistic scenarios predicted that the optimized perpendicular system may achieve a factor of 4 - 5 over the best longitudinal areal density, resulting in approximately 500 gb / in2. pessimistic evaluations consider that the advantages of the perpendicular recording are compensated by the disadvantages, resulting in the complete wash - out between the longitudinal and the perpendicular schemes. the realistic estimates are in the range of doubling the areal density achievable with longitudinal media, around 200 - 300 gb / in2 .
talking to people of hitachi gst, fujitsu, hitachi, and toshiba, they say that about 75% of hard disk drive shipments will be of perpendicular products. in 2010, probably all such products requiring memory will have adopted perpendicular recording drives. in this way, such large companies as toshiba, hitachi, fujitsu, and seagate technology are all concentrating on producing perpendicular disk drives .
for example, one of such problems is the thermal stability. as the recording densities increase, due to the constraint caused by the thermal stability, the track width decreases faster than both the down track and the perpendicular dimensions. the perpendicular recording write field decreases faster with the track width as compared to the longitudinal recording. although the tapered neck structure with a very small throat height on the write pole may be used to increases the write field significantly, the total write field still decreases when the recording density increases .
the tilted perpendicular recording design shown in figs. 2a and 2b can be used to produce large write fields and thus provide improved recording performance than conventional longitudinal recording and perpendicular recording. in order to enhance the write field magnitude, the write pole tip is designed to have a tapered neck structure with a very small throat height. the medium is designed to have the anisotropy easy axes tilted at a desired angle, e. g. , 30° or 45°, with respect to the perpendicular direction. the medium easy axes may be parallel to one another with a small cone angle of, for example, 5° or less .
the industry highest recording density in commercially available as of december 14, 2004 .
a read head for detecting the magnetized recording layer structure on the pillar tops .
due to above reasons, it is difficult for both the longitudinal recording and the perpendicular recording to exceed areal densities higher than 200 gbit / in 2. one of the main limitations in these systems is the low write field produced by various conventional write heads and thus media with a high medium anisotropy cannot be used to improve the recording performance .
the above tilted perpendicular recording may be used to achieve a high write field from write head to write highest anisotropy magnetic media. the media h k may be increased by a factor of about 1. 6 with this method. the neighboring tracks becomes more stable as the hk of the media increases. a larger write field, almost 50 - 80% higher than the highest write field in other systems, may be used in the present system. this high h k can be used to significantly solve thermal stability problem. for example, if the current grain sizes in other magnetic media are used, the tilted recording media may have an extreme long data decay time and can be practically used to store written data indefinitely. the media switching field distribution can be decreased by 80% . the switching speed, which may be at least 5 times faster than that in the perpendicular recording, is comparable with longitudinal recording. the tilted perpendicular recording allows for a large write field, almost 50 - 80% higher than the highest write field in other systems. for example, the write field can be close to the saturation field bs by introducing the tapered neck structure with very small throat height for single pole tip (spt) with sul. the tilted perpendicular recording significantly reduces the media switching field distribution so that a sharp transition can be achieved with a small transition width. this leads to a higher storage linear density. the tilted perpendicular recording also increases the media energy barrier at the track edge and the neighboring tracks as compared to conventional perpendicular recording. this allows for a reduction in the erase band by 50% or more in comparison with other recording methods. notably, a storage density at or above 1 tera bit / in 2 may be achieved in systems under this tilted perpendicular recording configuration. the tilted perpendicular recording may be suitable for various recording applications such as hard disk recording, pattern media, thermal assistant (pattern) media and other magnetic recording applications .
a perpendicular magnetic recording stack with a dual continuous layer and a method of manufacturing the same. the perpendicular magnetic recording stack includes a substrate, one or more magnetic granular recording layers, and a dual continuous layer having first and second continuous layers. the first continuous layer, disposed between the second continuous layer and the magnetic granular recording layers, has an intermediate lateral exchange coupling, which is higher than the lateral exchange coupling of the magnetic granular layers. the second continuous layer has a higher lateral exchange coupling than the first continuous layer .
a straightforward argument from the vertical field estimate is that the perpendicular pole head can in principle write media with twice the coercivity of the longitudinal medium. however, the realistic gain is much smaller due to different switching processes of longitudinal and perpendicular media. longitudinal grains have larger dispersion of easy axis orientation and are easier to switch, while perpendicular grains are typically well oriented in the vertical direction. in practice, the coercivity gain of a perpendicular recording system over longitudinal medium may be close to 50 - 70% .
6. the magnetic recording head as in claim 4, wherein the tapered neck has a straight profile on a trailing edge along the tracks of the recording medium .
referring back to fig. 8, the medium h k (h n) in the tilted perpendicular recording system is significantly larger than the medium h k (h n) in the perpendicular recording. in the cross track direction, any in - plane field changes the angle between the write field and the medium anisotropy direction away from 45°. as shown in fig. 4, the energy barrier of the medium grains increase with this angle. as go off track, the energy barrier increases. both the h k increases and the angle changes in the tilted perpendicular recording increase the energy barrier of the medium grains in the neighboring tracks. as a result, the adverse effect of the fringing field from the write head is reduced in the tilted perpendicular recording .
iwasaki, s. ,
perpendicular magnetic recording focused on the origin and its significance ,
ieee transactions on magnetics, 38 (4): 1609 - 1614, jul. 2002 .
implementations described and claimed herein provide perpendicular magnetic recording stacks with a dual continuous layer. in one implementation, the perpendicular magnetic recording stack includes a substrate, one or more magnetic granular recording layers, and a dual continuous layer having first and second continuous layers. the first continuous layer, disposed between the second continuous layer and the magnetic granular recording layers, has an intermediate lateral exchange coupling, which is higher than the lateral exchange coupling of the magnetic granular layers. the second continuous layer has a higher lateral exchange coupling than the first continuous layer .
a method of digital recording on a magnetic disk in which the bits are in a vertical arrangement instead of horizontal in order to take up less space. also called
vertical recording ,
toshiba and seagate introduced perpendicular recording drives in the 2005 - 2006 time frame. other drive vendors followed, and areal densities reached 400 gigabits per square inch by 2009 .
the demagnetization field in the perpendicular medium is small at the transition region. this allows writing narrower magnetic transitions and improves thermal stability of high density data (this is opposite to longitudinal medium). also, the non - linear transition shifts in the perpendicular medium are less critical, compared with longitudinal recording .
in may 2005, toshiba (japan) announced the shipment of a new music player with an installed hard disk drive, which for the first time in the world, used perpendicular magnetic recording. it was in 1977 that i first presented perpendicular magnetic recording at the international magnetic conference in los angeles. therefore, it took all of 28 years until that technology first appeared in the marketplace .
perpendicular flexible disk drive with a co - cr / ni - fe double layered recording medium and a single pole head. the auxiliary magnetic pole was located on the rear side of the disk .
the prior perpendicular recording is also limited by the signal to noise ratio (snr) due to the media switching field distribution, the small write field gradient, and effect of the magnetostatic interaction .
table 1 compares magnetic properties and recording parametric for perpendicular magnetic recording stacks having a single continuous layer with perpendicular magnetic recording stacks having a dual continuous layer. the magnetic properties include: coercivity field, h c, nucleation field, h n, and magnetization thickness product, mrt. the recording parametric include: writing plus erasure, wpe, reverse over - write, rev _ ow, on track bit error rate, pe, off track bit error rate, otc, media signal noise ratio, esmnr, and total signal noise ratio, esnr. as shown in table 1, the dual continuous layer improves the magnetic properties and recording parametric .
signal processing for readback signals has been changed. that is simply a matter of course because longitudinal recording was fundamentally appropriate for analog signals. therefore, standing on the concept of ‘complementarity’, which means the accomplishment of a total world by adding perpendicular recording to the conventional longitudinal recording world, is important. this is not a concept of ‘duality’ or a dual entity .
with reproduced waveforms indicating a single - peaked pulse resembling that of a conventional recording .
4. the magnetic recording head as in claim 1, wherein the tapered neck has a third tapered profile on a leading edge along the tracks of the recording medium .
5. the magnetic recording head as in claim 4, wherein the tapered neck has a fourth tapered profile on a trailing edge along the tracks of the recording medium .
base layers, i. e. all layers lying under the first magnetic recording layer
perpendicular recording can enhance the thermal stability in comparison with longitudinal recording. as the areal density increases, the medium grains in the down track and cross track dimensions are decreased in order to maintain good signal to noise ratio (snr). so the only way to enhance thermal stability for a given anisotropy medium is to increase the medium thickness. for a medium thickness greater than the grain diameter, the medium anisotropy directions are more likely to have perpendicular component as the thickness of the medium increases. however, there are still some intrinsic problems in perpendicular recording that cannot be easily solved satisfactorily .
the difference between longitudinal and perpendicular recording is the orientation of the media grains. in the case of longitudinal recording the grains magnetization is lying in the plane of the magnetic medium. when the media is magnetized by the recording head, the average magnetization is pointing in the down - track direction (figure 7. 1). when perpendicular head and media are used, the media grains are oriented in the “depth” of the medium and their magnetization is pointing either “up” or “down” .
once again, it is worth noticing, that the particular perpendicular roll - off curve strongly depends on the head and medium optimization. with all the advantages, draw - backs and limitations of the perpendicular recording system, recent experimental studies demonstrated about a 20 - 40% gains in the highest achievable areal density .
the principle of conventional magnetic recording is that magnetic fields are applied parallel to the plane of the magnetic medium. as described in this paper, the invention and development of a new method of placing the magnetized information perpendicular to the plane of the magnetic recording medium is presented. the yield in the mass production of high - density hard disk drives (hdds) for perpendicular recording is much higher than that of hdds for conventional recording. consequently, it is estimated that as many as 75% of the 500 million hdds to be shipped this year will use this technology .
victora r. (2001) perpendicular recording media. in: plumer m. l. , van ek j. , weller d. (eds) the physics of ultra - high - density magnetic recording. springer series in surface sciences, vol 41. springer, berlin, heidelberg
to understand the “u” - shape, we have to analyze the structure of the stray fields in the case of perpendicular recording. the schematic diagram of these fields is shown in figure 7. 10 .
these recording techniques, however, have difficulties to address various limitations or barriers for further increasing the storage densities, such as the thermal stability issue, the medium noise, the bit error rate limitations, and the limited data rate due to the limited medium switching speed and other limitations. the thermal stability issue is particularly limiting in the longitudinal recording. the large media switching field distribution and transition width can lead to certain limitations in the perpendicular recording in addition to the limitation due to the media switching speed problem. in both longitudinal and perpendicular recording, the write field decreases with track width and this aspect of such methods limits the storage densities. furthermore, the fringing field and the erase of neighboring tracks in both longitudinal and perpendicular recording are also barriers to achieving high storage densities.
perpendicular recording ( or perpendicular magnetic recording , pmr ) is a technology for data recording on hard disks . it was first proven advantageous in 1976 by shun-ichi iwasaki , then professor of the tohoku university in japan , and first commercially implemented in 2005 . the first industry-standard demonstration showing unprecedented advantage of pmr over longitudinal magnetic recording ( lmr ) at nanoscale dimensions was made in 1998 at ibm almaden research center in collaboration with researchers of data storage systems center ( dssc ) – a national science foundation ( nsf ) engineering research center ( ercs ) at carnegie mellon university ( cmu ) . 
perpendicular recording (or perpendicular magnetic recording, pmr) is a technology for data recording on hard disks. it was first proven advantageous in 1976 by shun-ichi iwasaki, then professor of the tohoku university in japan, and first commercially implemented in 2005. the first industry-standard demonstration showing unprecedented advantage of pmr over longitudinal magnetic recording (lmr) at nanoscale dimensions was made in 1998 at ibm almaden research center in collaboration with researchers of data storage systems center (dssc) – a national science foundation (nsf) engineering research center (ercs) at carnegie mellon university (cmu).
perpendicular recording (or perpendicular magnetic recording, pmr) is a technology for data recording on hard disks. it was first proven advantageous in 1976 by shun-ichi iwasaki, then professor of the tohoku university in japan, and first commercially implemented in 2005. the first industry-standard demonstration showing unprecedented advantage of pmr over longitudinal magnetic recording (lmr) at nanoscale dimensions was made in 1998 at ibm almaden research center in collaboration with researchers of data storage systems center (dssc) – a national science foundation (nsf) engineering research center (ercs) at carnegie mellon university (cmu).