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Yohei Takaoka,1,2 Rie Akaho,1 Ken Inada,1 Hiroyuki Muraoka,1 Choryo Hokama,1 Atsuko Inoue,1 Katsuji Nishimura1 1Department of Psychiatry, Tokyo Women’s Medical University, Tokyo, Japan; 2Department of Psychiatry, Kuki Suzunoki Hospital, Kuki, Saitama, JapanCorrespondence: Rie AkahoDepartment of Psychiatry, Tokyo Women’s Medical University, Tokyo, JapanEmail akaho.rie@twmu.ac.jpAbstract: Posterior reversible encephalopathy syndrome (PRES) is a clinical syndrome that presents as transient cerebral edema (vasogenic edema), usually on a background of hypertensive encephalopathy, puerperal eclampsia, or immunosuppressant drug use. We describe a case of PRES that arose in the context of a psychiatric disorder. The patient was a 26-year-old woman with schizophrenia who was hospitalized upon falling into a catatonic stupor and then suffered acute anxiety leading to impulsive polydipsia and subsequent water intoxication. She lost consciousness, and brain magnetic resonance imaging revealed a high density area, primarily affecting the cortex and subcortical white matter in areas in the occipital and parietal lobes, leading to the diagnosis. We did not treat the hyponatremia by means of aggressive sodium supplementation but rather balanced the extracellular fluid by continuous infusion of isotonic electrolyte replacement fluid. The patient’s level of consciousness improved gradually, but a total 141 days passed before hospital discharge was appropriate. The prognosis for PRES is generally favorable, but irreversible neurological damage can occur. We believe, therefore, that brain magnetic resonance imaging should be performed promptly whenever PRES is suspected and that timely, appropriate treatment is of utmost importance. If PRES is observed in a psychiatric patient, it is important to investigate whether the condition might have been caused by water intoxication and to treat the condition accordingly.Keywords: posterior reversible encephalopathy, schizophrenia, water intoxication

This paper presents a method of determining the transition curvature in magnetic recording, using only spin-stand measurements and a single read/write head. The method relies on finding an area of the disk in which the noise is in an as-deposited or bulk-erase state; the noise statistics can then be assumed to be independent of small changes in position across a track width. Trigger transitions are written on the disk and then the media noise is measured at many closely spaced positions across the track. From these multiple measurements, a 2-D picture of the noise referenced to the trigger can be created. This 2-D noise picture is distorted because of curvature of the trigger transitions. Assuming that the noise is truly stationary with respect to position, the underlying curvature of the trigger can thus be derived. On the basis of that derivation, any data pattern can be written and then read back and corrected for the known curvature on the trigger transitions. The paper compares the results obtained by this method with two different magnetic force microscope (MFM) observations. The new method shows, for example, that transitions written by a single-pole writer with a trailing shield writer have less transition curvature and transition noise than those written by a single-pole writer without any shield. Index Terms--MFM analysis, perpendicular magnetic recording, trailing shield head, written transition curvature.

In this work, we report on the determination of the optimum level of Si[O.sub.2] in [(CoCrPt).sub.1-x] [(Si[O.sub.2]).sub.x] perpendicular recording media. We have determined the optimum level via studies of magnetic viscosity which have been compared to recording properties. We find that the optimum level of Si[O.sub.2] is of the order of 10%. At this level, studies of the activation volume of reversal show that the grains become essentially exchange decoupled and that a further increase in the level of Si[O.sub.2] produces no further improvement in the decoupling. We also find that this level of Si[O.sub.2] corresponds to optimum recording performance and that increasing the level of Si[O.sub.2] further results in the production of a system with smaller grains where thermal loss is observed to increase dramatically. Index Terms--Activation volume, intergranular coupling, magnetic characterization, perpendicular recording media.

Recent simulations of coupled granular/continuous (CGC) perpendicular media are reviewed, and mechanisms previously shown to reduce bit transition irregularity are clarified using a three-dimensional micromagnetic model that includes a simple representation of grain shape irregularity. Increasing intergranular exchange coupling is found to resolve magnetic clusters at the bit transition into smaller switching units. This is shown to reduce the amplitude and cross-track correlation length of the transition irregularity. The signal-to-noise ratio (SNR) of high-density granular media and CGC media is optimized with respect to intergranular exchange coupling. Depending on the media parameters used, the recording properties of granular and CGC media are found to differ, with CGC providing greater SNR. Preliminary experimental data are presented and found to support the results obtained from simulations. Index Terms--Coupled granular/continuous (CGC) media, exchange coupling, micromagnetic simulation, perpendicular magnetic recording.

Thermal stability of coupled granular/continuous (CGC) perpendicular media is supported by fundamental modeling and experimental results, including spin-stand testing. By incorporating the interlayer exchange coupling into the model, the simulation result suggests that the CGC structure is capable of achieving the energy barrier of [K.sub.u]V/[k.sub.B]T required for 1 Tbit/[in.sup.2] recording density. To demonstrate the CGC approach, we investigate a new class of CGC perpendicular media consisting of a Pt-rich CoPtCr layer with poor Co-Cr phase segregation and a thin Pt layer. The addition of these layers improves the nucleation field of the Co[Cr.sub.18][Pt.sub.12] medium from +420 to -600 Oe and the thermal decay of the output is reduced from 2.23% to 0.10% per decade. Unity squareness was obtained by using a thin Pt capping layer and resulted in a small decay rate of 0.21% per decade. The new CGC media showed no degradation of SNR compared to the base granular medium. Similar to CGC media utilizing a multilayer capping structure, the CGC medium with a Pr. rich CoPtCr or Pt capping structure improved the thermal stability without compromising SNR. The simplicity of these new CGC structures also greatly simplifies the deposition process. Index Terms--Continuous layer, granular layer, perpendicular media, Pt layer, signal-to-noise ratio, thermal stability.

A new type of thin film inductive single-pole head for perpendicular magnetic recording has been developed to provide a writing head for perpendicular double layer media. The head consisted of a main pole, three thin-film conductive layers to drive the pole and a return path pole. A low inductance of around 1.5 nH and a small saturation magneto-motive force of less than 0.025 [AT.sub.0-p] was obtained. The [D.sub.50] was 180 kFRPI with an MR head of 210 nm shield separation. The error rate at 310 kFRPI was [10.sup.-6]. Head induced erasure, which is an issue for the single-pole head, was also investigated by experiments and calculations. Around 10% output reduction in 20 Oe stray field was confirmed. Computer simulation predicted an improvement by reducing the permeability of the medium's underlayer. Index Terms - Inductive head, perpendicular magnetic recording, single-pole head, double layer media.

Magnetization transitions, readback waveforms, and transition jitter are formulated for Voronoi modeling using error functions. Suitable coefficients for the error functions are provided by the parameters of the granular media, i.e., average grain diameter and grain size distribution. TEM images of real media are used to confirm the fitted results. Random grain positions and uniform switching field distribution are assumed. Readback waveforms for isolated transitions are calculated by reciprocity. The pulse width, T50, is formulated from the medium parameters and readback conditions. An error function with the same T50 and slope at the transition center is a good fit. An analytical expression for jitter noise is presented comprising grain size and track width parameters. [ABSTRACT FROM AUTHOR]

A study of the thickness dependence of the uniaxial magnetic anisotropy [K.sub.u] of Co-Pt perpendicular films deposited on Ru seed layers was extended over a wide range of Pt content from 10 to 30 at%, to further investigate the origin of the significant increase in [K.sub.u] on reducing the film thickness, which was previously reported for [Co.sub.80][Pt.sub.20]/Ru films. [K.sub.u] increased significantly as the thickness decreased in all series of films with various Pt content. The rate of increase of [K.sub.u] with reducing thickness became increasingly large as the Pt content decreased. It should be noted that the [K.sub.u] of 2-nm-thick films was an almost constant 2 x [10.sup.7] erg/[cm.sup.3] over the range of Pt contents studied, although [K.sub.u] was maximized at 25-30at%Pt content for films thicker than 5 nm. Experimental results suggest that the increase in [K.sub.u] on reducing the thickness was mostly related to a reduction of the hcp Co-Pt lattice c/a ratio. Index Terms--Co-Pt films, fcc volume fraction, hcp lattice, lattice deformation, Ru underlayer, surface anisotropy, uniaxial magnetic anisotropy.

The switching fields and thermal stability of CoPt/Ru dot arrays with various dot thickness [delta] (5-20 nm) were experimentally investigated as a function of the dot diameter, D, (130-300 nm). All dot arrays showed a single domain state, even after removal of an applied field equal to the remanence coercivity [H.sub.r]. The angular dependence of [H.sub.r] for the dot arrays indicated coherent rotation of the magnetization during nucleation. We estimated the values of the 'intrinsic' remanence coercivity Ho obtained by subtracting the effect of thermal agitation on the magnetization and the stabilizing energy barrier to nucleation [E.sub.o]/([k.sub.B] T). The variation in [H.sub.o] as a function of [delta] and D was qualitatively in good agreement with that of the effective anisotropy field at the dot center [H.sup.eff.sub.k] (r = 0), calculated taking account of the demagnetizing field in the dots. The ratio of [H.sub.o] to [H.sup.eff.sub.k] (r = 0) for the dot arrays with [delta] = 10 nm increased from 0.53 to 0.70 as D decreased from 300 to 140 nm, and no significant difference in the [H.sub.o] to [H.sup.eff.sub.k] (r = 0) ratio due to the difference in 6 was observed. On the other hand, [E.sub.o]/([k.sub.B] T) decreased as [delta] decreased. [E.sub.o]/([k.sub.B] T) increased slightly as D decreased, but, was not so sensitive to D over the present D range. Index Terms--CoPt perpendicular films, dot arrays, remanence coercivity, single domain, thermal stability, patterned media.

The first and second order uniaxial magnetic anisotropy, [K.sub.u1] and [K.sub.u2], and the saturation magnetization, [M.sub.s], of [([Co.sub.100-X][M.sub.X]).sub.100-Y][Pt.sub.Y] perpendicular thin films were examined, in order to improve the magnetic properties of CoCrPt-Si[O.sub.2] media by replacing Cr with M. Fourteen kinds of M elements were examined, but we mainly focus on films with M = Cr, Mo, Ru, W and Re in this paper, since the other elements significantly reduced [K.sub.ul], [K.sub.u2] or the Ku/[M.sub.s] ratio. The use of the M elements, instead of Cr, did not result in any significant increase in the values of [K.sub.ul], [K.sub.u2], and the [K.sub.u]/[M.sub.s] ratio. On the other hand, [K.sub.ul] and [K.sub.u2] of CoPt binary films had a greater dependence on the seed layer materials used (Ru, Pd, Re, Pt, Au, Ir and Cu). The c/a ratio of the hcp-CoPt lattice varied significantly with the seed layer materials used probably due to the epitaxial growth of CoPt.[K.sub.ul] decreased and [K.sub.ul] increased as the c/a ratio increased. The use of specific seed layer materials was more effective at controlling the magnetic anisotropy of CoPt based perpendicular thin films, rather than the addition of M element to the CoPt. Index Terms--c/a ratio, CoPt based ternary alloy perpendicular films, perpendicular recording media, saturation magnetization, seed layers, uniaxial magnetic anisotropy energy.

The magnetic properties and recording performance of hard/soft stacked media consisting of a magnetically hard 9-nm-thick (CoPt)-Si[O.sub.2] layer underneath a thin (2-3 nm) soft granular layer were studied. Experimental results indicated that an increase in the mean value of saturation magnetization of the soft layer was very effective at improving the recording resolution [D.sub.50] due to an increase in the slope of magnetization curve [alpha]. The use of a Co-Si[O.sub.2] layer, which has the highest in the present study, resulted in the highest [D.sub.50] value. It is likely that the increase in [alpha] was mainly caused by the demagnetization field in grains due to the difference between and the mean value of saturation magnetization of the hard layer, . Moreover, it was successfully demonstrated that the magnetization reversal of (Co-Pt)-Si[O.sup.2]/Co-Si[O.sub.2] stacked media changed systematically as theoretically predicted on reducing the interracial exchange coupling by using NiFeCr-Si[O.sub.2] or Pt-Si[O.sub.2] interlayers. The reduction of remanence coercivity [H.sub.r] was achieved by controlling the thickness and film composition of the interlayer, moreover, a high- enhanced the [H.sub.r] reduction. The [H.sub.r] reduction improved recording writability without degrading [D.sub.50], the signal to medium noise ratio S[N.sub.m]R and thermal stability. Index Terms--Hard/soft stacked media, interracial exchange coupling, large saturation magnetization, perpendicular recording media, recording resolution, recording writability, remanence coercivity, signal to medium noise ratio.

The switching field distributions (SFD) of CoPtCr-Si[O.sub.2] perpendicular media as a function of Pt content were characterized by subtracting the effect of thermal agitation, and discussed in relation to the microstructure. DC demagnetizing (DCD) magnetization curves and minor dc demagnetizing (M-DCD) magnetization curves were measured at applied field sweep rates of ~10 Oe/s and ~[10.sup.8] Oe/s. We estimated the width of SFD, [DELTA] SFD, from the difference between the DCD and M-DCD curves, and defined them as [DELTA] [H.sub.r]/[H.sub.r] (at 10 Oe/s) and [DELTA] [H.sup.P.sub.r]/[DELTA] [H.sup.P.sub.r] (at ~108 Oe/s). The values of [DELTA] SFD characterized by subtracting the effect of thermal agitation, [DELTA] [H.sub.o]/[H.sub.o], were nearly half those of [DELTA][H.sub.r]/[H.sub.r] for 10-nm-thick media. [DELTA][H.sub.o]/[H.sub.o] was about 0.10 at 10 at % Pt content, and increased as the Pt content increased, reaching 0.17 at 30 at % Pt content. The increase in [DELTA][H.sub.o]/Ho was probably caused by an increase in the stacking fault density and the formation of fcc layers in the hcp CoPtCr lattice. A simple calculation based on the coherent switching of magnetization revealed that the c-axis distribution results in [DELTA][H.sub.o]/[H.sub.o] of about 0.08, independent of Pt content. These results suggest that the [DELTA] SFD due to the grain-to-grain anisotropy field variation was small, only 0.02-0.03. Index Terms--CoPtCr-Si[O.sub.2] perpendicular recording media, film composition, pulse field, switching field distribution, thermal agitation of magnetization.

The magnetic properties of dot arrays made of CoPt/Ru perpendicular films (20 nm thickness) were examined as a function of Pt content. The CoPt dot arrays with a dot size D of 140 nm showed a single domain state, after removal of the applied field equal to [H.sub.r]. [H.sub.r] decreased from 5.2 kOe to 3.0 kOe as the Pt content decreased from 20 at% to 14 at%. The angular dependence of [H.sub.r] for these dot arrays indicated coherent rotation of the magnetization during nucleation. The effective magnetic anisotropy, including the demagnetizing energy due to the dot shape, [K.sup.eff.sub.u], decreased as the Pt content decreased, resulting in the [H.sub.r] reduction. The values of the switching volume for nucleation, [V.sub.sw], evaluated from the stabilizing energy barrier [E.sub.0], were a few percent of the dot volume. The switching diameter for nucleation, [D.sub.sw], increased slightly as the Pt content decreased, which was qualitatively in good agreement with the increase in the exchange length of magnetization. The value of [E.sub.0]/[k.sub.B]T ([k.sub.B] is the Boltzmann constant and T is the absolute temperature) reduced as the Pt content decreased; however, [E.sub.0]/[k.sub.B]T still had a high of 440 even at 14 at% Pt content. We successfully demonstrated the reduction of [H.sub.r] for CoPt/Ru patterned films on reducing the Pt content, while simultaneously maintaining a high thermal stability. A calculation based on the experimental results suggested the potential recording density of CoPt/Ru dot arrays used for patterned media to be over 1 Tb/[in.sup.2]. Index Terms--CoPt/Ru perpendicular films, dot arrays, patterned media, remanence coercivity, single domain, thermal stability.