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The thin-film power amplifier module for wide-band code division multiple access was designed and fabricated using the magnetic thin film as magnetic core of choke inductors. CoFeSiO--Si[O.sub.2] multilayer granular films showing high resistivity and good magnetic properties were applied to the module. Inductance value increased about 30% by application of magnetic films, and occupation area and series resistance were also reduced by 20%. The obtained module size was 3.0 mm x 3.5 mm, which was much smaller than the conventional power amplifier module, since the bias circuit was formed on the same silicon substrate. Index Terms--Choke inductor, magnetic film, power amplifier module, thin-film inductor.

We developed a novel piezoelectric microactuator for dual-stage actuator systems in magnetic disk drives. This microactuator is based on the shear deformation of piezoelectric elements, and drives the head suspension assembly. The actuator is suitable for thin devices, and is easily manufactured because of its simple stack configuration. We installed the microactuator in a 2.5[inches] prototype drive, and evaluated the servo system of the dual-stage actuator. This paper describes the structure of our piezoelectric actuator, its mechanical characteristics, and the evaluation of the dual-stage actuator servo system. Index Terms - Dual-stage actuator, magnetic disk drives, microactuator, piezoelectric actuator, shear mode.

A systematic investigation of structural and magnetic properties of FePt/FeRh bilayers on dependence of temperature has been carried out. The transition temperature of single FeRh layer was higher than that of FePt/FeRh bilayer. A sharp decrease in coercivity is observed at transition temperature for FePt/FeRh bilayer. The thickness FePt and FeRh dependence of exchange bias field and unidirectional anisotropy constant are discussed. Of interest is that the exchange bias effect appears in FePt/FeRh bilayer and unidirectional anisotropy constant is very large up to 1 erg/[cm.sup.2], suggesting that this system can be applied to spin-valve sensors and heat assisted magnetic recording medium. Index Terms--Exchange bias, FePt/FeRh bilayer, FeRh thin films, first-order phase transition.

We fabricated toggle magnetic random access memories with clad writing lines. First, we evaluated the structures and magnetic properties of sputter-deposited cladding layers. The substrate bias during the deposition affected not only the sidewall coverage, but also the crystallinity and magnetic properties of the cladding. The optimized clad lines reduced the writing current to as low as 50% of that of unclad lines. Moreover, the writing current deviation divided by the average current of magnetic tunnel junction cells with clad lines was as low as that with unclad lines. Using the optimized clad lines, we constructed memory arrays with a large operating margin and reduced switching current. Index Terms--Clad line, magnetic property, structure, toggle MRAM, writing current.

The role of Fe underlayer on the magnetic properties of [Fe.sub.3] Pt has been studied. Thin films of [Fe.sub.3] Pt are grown epitaxially onto [Al.sub.2][O.sub.3] (00 x 1) substrate by electron beam evaporation. These samples grown at around 400[degrees]C show (111) orientation and exhibit large 6-fold basal plane magnetic anisotropy ([10.sup.7] erg/cc) which could he enhanced by introducing Fe underlayer. Based on perpendicular hysteresis curves measured by magneto-optical polar Kerr effect and the anomaly of the perpendicular torque curves, it is interpreted that a large perpendicular magnetic anisotropy in [Fe.sub.3] Pt thin films is generated by Fe underlayer. Index Terms--Azimuthal scan, magneto-optical polar Kerr effect, six-fold basal plane magnetic anisotropy.

A new MSR-ROM method for high density recording utilizes the difference in coercivity between 'rough' and 'smooth' areas in a disk. This method is advantageous for mass production and for the compatibility with erasable magneto-optical recording using MSR. A recording density of 5 Gbit/[inch.sup.2] is expected in this method, the same as the double mask type MSR technique in rewritable disk. This paper describes the principle of MSR-ROM and the results of a basic experiment.

We developed a new piezoelectric microactuator for dual-stage actuator systems in magnetic disk drives. This actuator exploits the shear mode of piezoelectric elements and drives the head suspension assembly. This paper describes the structure of our piezoelectric actuator, its mechanical characteristics, and the experimental results of a life test after driving the piezoelectric elements in an atmosphere of high temperature and humidity. Index Terms - Magnetic disk drives, micro-actuator, piezoelectric actuator, shear mode.

The DC erasure process in a CoCrTa medium used for 0.8 Gbit/[in.sup.2] recording is investigated and compared with a CoCrPtTa medium capable of supporting 5 Gbit/[in.sup.2]. All-ones patterns up to 250 kfci were imaged in the remanent state after the application of in situ magnetic fields parallel to the tracks. For CoCrTa, the averaged MFM signal drops faster with field compared to the bulk DC demagnetization (DCD) curve. This is different from CoCrPtTa where the MFM signal fits the DCD curve for fields applied along the track direction. For both media, the normalized MFM signal reduction with field is independent of recording density indicating reduced average demagnetizing fields. Index Terms - Magnetic recording media, DC erasure, demagnetizing fields, magnetic force microscopy.

CoCrPt media with 20 nm thickness are fabricated at low temperatures on plastic disks using Cr and Si[O.sub.2] underlayers and on glass substrates using a Cr underlayer. The fabrication condition is optimized for high coercivity of 2.2 kOe on plastic and 2.4 kOe on glass. The dependence of magnetic properties on Ar pressure and sputtering power of CoCrPt is discussed for the media on plastic disks in comparison with the glass case. The micromagnetic properties such as Barkhausen volume and [Delta]M are discussed. Recording properties of the media on plastic disks deposited under different fabrication conditions are also discussed, and are found to be consistent with micromagnetic properties. Index Terms - Magnetic Recording Media, Micromagnetics, Plastic Substrates, Recording Performance.

In this study a quantitative analysis of magnetic force microscope images of bit transitions in media suitable for 5 Gbit/[in.sup.2] applications is made. Bit transitions written between 10 kfci and 400 kfci and DC erased domain features have been observed by using two types of MFM tips. Transition widths, the size of percolations in transitions and the cross track correlation length relative to DC erased domain features are reported upon. A comparison between cross track correlation lengths and media noise is made along with a discussion of the domain structure of tracks and percolations between bits written at very high kfci.

The dc erasure process in a 5 Gbits/[in.sup.2] medium is investigated using magnetic force microscopy (MFM). 50 to 250 kfci patterns were imaged in the remanent state after application of in situ magnetic fields perpendicular [H.sub.[perpendicular to]] and parallel [H.sub.[parallel to] to the tracks. Degradation of bits is observed to start at the track edges and the transitions. Decay at the transition tends to occur locally at many places and propagates into the bits with opposing magnetization relative to [H.sub.[parallel to]]. For [H.sub.[perpendicular to]], decay occurs on both sides of the transition and the written bits persist at higher fields compared to the application of [H.sub.[parallel to]]. For the [H.sub.[parallel to]] case, the averaged MFM signal for 50 to 250 kfci patterns fit the bulk dc demagnetization curve suggesting the reduced effect of demagnetizing fields.

Starting and driving methods of contactless power transmission to electric vehicles are proposed. By employing rectangular and spiral coils for primary and secondary windings, respectively, for contactless power station. We could transmit electric power over 200 W to our fabricated EV motor setup and verify the actual operation on it. The EV is a compact prototype driven by CLPS, loaded with a light-weig ht battery. The battery supplies a part of transient current arising from starting and acceleration of EV. We could actually drive the CLPS-powered prototype at 30km/h for the overall energy consumption of 100W. Driving test with and without CLPS using '10-mode' driving schedule were executed and compared.

The texture and the easy axis of magnetization of Strontium ferrite (Sr[Fe.sub.12][O.sub.19]) thin films can be controlled by changing power of rf sputtering. In-plane magnetic anisotropy is developed at a sputtering power of 330 W (7.5 W/[cm.sup.2]), whereas strong perpendicular magnetic anisotropy (Ku [approximately] 1 x [10.sup.6] erg/cc) is induced at 60 W power (1.3 W/[cm.sup.2]). Further control over coercivity and morphology can be achieved by changing the ratio R, between oxygen and argon in the sputtering gas. Coercivity decreases with R. Films deposited without oxygen exhibit higher coercivity and less intergranular interaction as compared to films sputtered with oxygen.

The thermal stability of high density written bits in a 5 Gbit/[in.sup.2] CoCrPtTa/CrMo medium is examined using a magnetic force microscope. Images of the same 0.8 [[micro]meter]-track all-ones pattern were taken before and after various anneal schedules. Written bits, which for the measured magneto-crystalline anisotropy and switching volume, are predicted by simulation studies to be thermally unstable reveal no significant degradation with annealing up to 490 K for 2 hours. This discrepancy emphasizes the need for more realistic theoretical models.

Both the magnetization and perpendicular magnetic anisotropy at 300K decrease with Bi content x in ([Co.sub.1-x][Bi.sub.x])/Pt multilayers, whereas the magnetization increases with x in (Co/[Pt.sub.1-x][Bi.sub.x]). The maximum magneto-optical Kerr rotation increases with x up to x = 0.12, then decreasing with x for (CoBi/Pt). On the other hand, the rotation decreases with x in (Co/PtBi). The photon energy for the maximum Polar Kerr rotation becomes smaller with x for (Co/PtBi), but it remains unchanged for (CoBi/Pt).

We have investigated the effect of grooves milled by argon ions in soda lime glass substrates on the magnetic behavior of amorphous TbFeCo films deposited onto these substrates. The domains are shown to expand along the grooves when the groove depth exceeds 10 nm. The effect originates from the difference in the coercivities of the film on the land and on the groove, as well as from the pinning of domain walls by the side-walls of the grooves.

A systematic study on magnetic and magneto-optical properties of FeCo/Pt multilayer films has been performed. The FeCo/Pt multilayer exhibits a large intrinsic perpendicular anisotropy Ku, which is nearly same value as Co/Pt multilayer films. The surface anisotropy Ks and the volume anisotropy Kv are found to noticeably depend both on the Pt layer thickness and on the FeCo layer thickness. The saturation magnetization is found to exceed the value for pure FeCo alloy at low temperature. The value of the Kerr rotation angle theta(sub k) is lower than that for Co/Pt films in 250 < gamma < 800nm while it is larger than that for Fe/Pt films.

Sputtered Co/Pt multilayers grown on etched SiNx buffers exhibit large perpendicular magnetic anisotropy and show a striking thickness dependence of the perpendicular coercivity. HC is perpendicular to of a series of Nx(0.3nmCo/1.1nmPt) multilayers varies from 0 to 3.3kOe, with a linear rise in the range 2 less than or equal to N less than or equal to 13 and saturates in the range 13 less than or equal to N less than or equal to 30. This behavior does not correlate with the column diameters and vertical grain sizes determined from XTEM and XRD measurements and is interpreted in terms of nm rather than Micrometer scale defects, which are responsible for domain wall pinning and nucleation in the present films.

A highly sensitive high frequency carrier-type magnetic field sensor based on the giant magnetoimpedance effect has been developed. It has been combined with a high frequency carrier suppressing circuit to reduce carrier phase noise dramatically. Highly sensitive magnetic field resolution of 8.8 x [10.sup.-7] Oe (8.8 x [10.sup.-11] T) was demonstrated. Index Terms--Carrier suppression, giant magnetoimpedance, high frequency carrier, magnetic field sensor, phase noise.

A near-field MO recording was done at a wavelength of 680 nm using a super-hemispherical SIL flying head. The SIL optical system has a designed NA of 1.46. The SIL can write and read marks to a minimum length of about 0.15 [micro]m. The optical readout characteristic with the SIL is not very sensitive to air gaps if the air gaps are kept below about 130 nm. Index Terms--Air gap, high numerical aperture (NA), magneto-optical (MO) media, near-field optical recording, solid immersion lens (SIL) flying head.

The intrinsic perpendicular magnetic anisotropy constant [K.sub.u] of [([Co.sub.100-x][Fe.sub.x]).sub.50][Pt.sub.50] (0 [is less than or equal to] x [is less than or equal to] 100) alloy thin films is determined at room temperature. It is found to increase with order parameter S, and decrease with the tetragonality c/a for all compositions. The estimated [K.sub.u] values obtained by the extrapolation to S = 1 are nearly identical for x from 0 to 56, but increase for x beyond 56. The polar Kerr rotation is found to become more enhanced for photon energies near 1.4 ~ 3.5 eV and 4 ~ 6.8 eV with increasing x. Observations of domain structures in [Fe.sub.50][Pt.sub.50] thin films reveal an induced in-plane magnetic anisotropy when the thickness exceeds 1000 [Angstrom]. Index Terms--c/a, [([Co.sub.100-x][Fe.sub.x]).sub.50][Pt.sub.50], order parameter, perpendicular magnetic anisotropy.

A near field optical technique based on combined supersphere solid immersion lens (SIL) with magnetic field modulation (MFM) recording is described. A better resolution is achieved by using SIL with MFM recording in comparison with light intensity modulation (LIM). A recorded mark as small as 0.3 [micro]m x 0.2 [micro]m could successfully be detected. These marks were readout by the SIL head with a typical signal to noise ratio value of 36 dB. The present study demonstrates the capability to achieve a very high areal density beyond 20 Gb/[in.sup.2]. Index Terms--Magneto-optical recording, near field optics, numerical aperture (NA), solid immersion lens (SIL).

A high numerical aperture Solid Immersion lens (SIL MO) magneto-optical recording system based on supersphere SIL approach is described. Effects of SIL on the recording performance of the magneto-optical system are analyzed. It is found that effective numerical aperture as high as 1.46 can be achieved using a contact SIL operation mode and evanescent coupling optimized TbFeCo recording media. A novel quadrilayer media design with CNR value of 50 dB is proposed. Index Terms--magneto-optical recording, near field, solid immersion lens, numerical aperture, CNR

The activation volume ([V.sub.a]) and its correlation to media noise in high-density longitudinal recording media are investigated. Magnetization decay is observed to be non-linear with In(t) for the media studied, and the necessity for using a correct method for estimating a fluctuation field is emphasized. The activation volumes are shown to increase with decreasing reversing fields and the values of [V.sub.a] at low fields (of a few hundred Oe) are significantly higher than those at the coercivity. Thus, the collective behavior of the magnetic grains is influenced not only by the intergranular interactions but also by the stray fields. The media noise of different media is correlated to the [V.sub.a] values at low fields. Index Terms--Longitudinal recording media, Thermal activation, Activation volume, Media Noise.