CoCrTaPt/Cr thin-film magnetic recording media were prepared by dc magnetron sputtering onto circum-ferentially textured NiP/Al substrates at various substrate temperatures and substrate bias voltages. The in-plane crystallographic structure analyzed by laboratory X-ray diffraction and grazing iwas ncidence X-ray diffraction using synchrotron radiation, and the correlation between the in-plane crystallographic structure and coercivity was studied. The coercivity was found to depend on both the in-plane c-axis population and strain. This suggests that both magnetocrystalline anisotropy and the inverse mag-netostrictive effect govern the coercivity and magnetic anisotropy. However, the in-plane crystallite size of a Co alloy layer was the same for any deposition parameters.

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CoCrTa/Cr magnetic films on Si(100) substrates with and without HF pre-treatment were prepared by dc magnetron sputtering. It was found that the coercivity was increased by HF pre-treatment of the Si substrate for Cr underlayers of various thicknesses. The microstructure analyses of the magnetic films using XRD. FE-SEM,and TEM showedthat the crystallinity and the orientation of the c-axis in the film plane were enhanced and that the grain size was increased by HF pre-treatment.

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The effect of the direction of MFM tip's magnetization on MFM images and the analysis of the in-plane magnetic field for longitudinal magnetic recording media were examined. The in-plane magnetic stray field was effectively detected by magnetizing the MFM tip to the in-plane direction. The MFM contrast of magnetic transition region was drasti- cally changed and a zigzag transition was clearly observed by changing the angle between the magnetized direction of the MFM tip and the track direction of the media. The magnetic fine structure of the media is also discussed.

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The effects of the annealing time on barium ferrite (BaM) thin films were studied. After deposition without substrate heating, the films were annealed at 900°C in air. Films annealed for 45 s. or longer were found to crystallize and had a tendency for the c axis to be oriented in a perpendicular direction. Films with high coercivity and high squareness ratio of about 3 kOe and 0.8, respectively, in the perpendicular direction could be prepared in an annealing time of 60 s. The grain size and the roughness of the surface were increased with the annealing time.

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Co-γFe₂O₃perpendicular magnetic recording media were preparedby the CoO-Fe₃O₄single-1ayer deposition method, which is more suitable for mass production than the CoO/ Fe₃O₄ multilayer deposition method. Moderately <100>-oriented Co-γFe₂O₃media with intermediate perpendicular anisotropy (K_u=6.0 × 10⁵erg/cm³) were prepared with a wide range of film thicknesses and oxygen partial pressure used in deposition of NiO underlayers. These media showed a superior high-density recording performance comparable to that of highly <100>-oriented Co-γFe₂O₃ media with large perpendicular anisotropy (K_u=1.4 × 10⁶ erg/cm³). It is surmised that the superior performance of these media was supported by the longitudinal magnetic component as well as the perpendicular one.

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The effect of a CoO underlayer on Co-O films deposited obliquely is investigated through magnetic measurements and micro structure observations of the films. The under-layer makes the coercivity of the films high. Films with the underlayer have high uniaxial magnetic anisotropy along columnar grains, becauseof the c-axis preferred orientation of hcp-Co. The granular texture of the underlayer promotes separation between columnar grains growing obliquely.

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The read/write performance of obliquely oriented Co-O thin-film tapes was investigated with regard to the aniso-tropy dispersion. Highly uniaxial tapes 1 and 2 exhibited considerable output enhancement when recorded with an asymmetric MIG-type head with saturation flux densities on the trailing and leading edge poles of 1.3 T and 1.0 T, respectively. This enhancement is thought to have been causedby the asymmetry of the head field in relation to the gap center, with a larger field gradient on the trailing side, resulting in a narrower transition width. On the other hand, output enhancement with the asymmetric head was not observed in tape 3, which had larger anisotropy dispersion. It is suggested that the easy direction of tape 3 curves in the film thickness direction and is oriented more perpendicularly in the surface region of the tape, where demagnetizing action by the head field on the trailing side decreases the effective moment of the recorded bits.

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The properties of SmCo/Cr bilayer films with underlayers prepared at various Ar gas pressures (P_Ar) and substrate temperatures (T_s) were studied. When P_Ar was increased from 0.13 Pa to 1.06 Pa or T_s was increased from 50°C to 190°C, the intensity of the X-ray diffraction line from the Cr(110) plane became weak. The coercivity, squareness ratio, and coercivity squareness ratio of the SmCo layer increased with an increase in the intensity of X-ray diffraction. The magnetic properties of the SmCo layer were found to improve according to the emphasized crystal structure of the Cr underlayer.

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Measurement techniques used to study dispersions are discussed. The results may be used to infer the fraction of magnetic material that is free to rotate and the average size of pigment entities in the dispersion. This can be a guide to the quality of the dispersion.

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A new technique for creating a thin-film head with a controlled domain structure was investigated. The difference between the thermal expansion coefficients of the magnetic film and the photoresist insulation layer greatly affects the stress distribution across the upper magnetic core after annealing. Tensile stress is induced in the lower part of the upper magnetic core, and compressive stress is induced in the upper part of the core. The composition distribution of NiFe alloy across the upper core can be controlled by means of the electroplating conditions. Consequently, magnetoelastic effect anisotropy can be induced to stabilize the domain structure of the upper magnetic core. This new technique was used to fabricate a thin-film head with low wiggle noise.

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We investigate multilayer resist processes using reactive ion etching (RIE) for the narrow-track resist frame of thin-film heads. In terms of the shape of the resist, the three-layer resist (photoresist/SiO₂/photoresist) process is better than the two-layer resist (Si containing resist/photoresist) process. Reducing the pressure of O₂ plasma during RIE causes the residue of the resist to vanish. A resist frame with a width of 1μm and a height of 6μm can be produced by using the three-layer resist process. Plating was performed within this frame.

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Hysteresis and baseline shift are studied in soft-adjacent-layer-biased MR sensors with abutted quasi-permanent magnetic bias. The magnet consists of NiFe/NiMn exchange-coupling films, which apply longitudinal bias field to an MR sensor. Abutted bias-magnet structures with various taper angles fabricated, and the overlap lengths were measured as the length of the MR flat active region covered by the longitudinal bias films. The hysteresis measured from the transfer curve decreases with decreasing overlap length. The repeatable baseline shift in the readback signal was also improved by decreasing the overlap length in the MR sensor.

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Instability is studied for an SAL-biased MR head with abutted permanent magnets. An MR head with insufficient longitudinal bias is simulated by demagnetizing the permanent magnets. The values of the output and the peak asymmetry fluctuate between two states, one with high output and small asymmetry, and the other with low output and highly negative asymmetry. In the low output state, microtrack profile measurements taken while varying the value of the sensing current show the MR layer to be in a buckling domain structure. This causes a hysteresis in the output versus sensing current curves. The buckling domain structure can be changed into a single-domain structure by increasing the sensing current above a certain level. This brings the head back into the high-output state.

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The read performance of spin-valve heads with overlapping leads is studied by using a micromagnetic model. In the case of hard biased spin-valve heads without an overlapped region, the sensitivity (output per lead distance) falls significantly with decreasing lead distance because of the existence of dead zones at both ends of the track. However, heads with 0.5-μm-wide overlapped regions at the ends of the sensing film have high sensitivity even if the lead distance is reduced to 0.5μm. Their output for an effective track width of 1.0μm is 30% larger than that of heads without the overlapped region when the heat generation is the same. Their output has a smaller dependence on the longitudinal bias strength, indicating a larger margin for the longitudinal bias. Spin-valve heads with overlapping leads are promising for high-track-density recording.

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Track-edge noise in a written track and a partially dc-erased track was analyzed to clarify the edge noise properties of a side-erased band. It was found that the track-edge noise power and its noise components in a partially erased track are equal to those in a written track. The track-edge noise power in a side-erased band is the summation of the transition-edge noise power of old track, the overwritten track, and the bit-edge noise power.

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The effects of the structure of a conventional NiP/Al substrate on shock resistance were investigated. In this study, a 2.5-inch-type hard disk drive with a thin-film 70%-micro-slider head was used. The tested shock was supplied by a pendulum shock-testing machine with a half-sine shock pulse and a duration of l.0 ms. We defined the shock resistance as the maximum acceleration in a shock for which head slap was not formed. The results showed that the shock resistance increased with increasing hardness of the Al alloy and thickness of the NiP underlayer.

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The stiction force between a medium and an a-SiO_x: H film (hydrogenated amorphous SiO_x) overcoat slider (50% MIG head) was investigated by means of a newly constructed stiction force tester. The stiction force was estimated from the first pulse width of the current signal of the tester's, spindle motor, because the first pulse width is proportional to the load force. No significant increase in the stiction force was observed in the range from 50% to 85%RH in the case of the a-SiO_x: H film overcoat slider. However, the stiction force of a non-overcoat slider (CaTiO₃ slider) increased drastically at 85%RH to almost double the stiction force of the a-SiO_x: H film overcoat slider. Furthermore, the low friction coefficient of the a-SiO_x: H overcoat slider was still maintained even after 50,000 CSS cycles in high humidity conditions, such as 85%RH. Therefore, the a-SiO_x: H overcoat slider has great potential for application in the HDD industry.

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The authors investigated head-disk interface design for in-contact recording systems using liquid bearing. The design concept of the liquid bearing is to realize a low bouncing height of sliders by using the meniscus attractive force of the lubricant between slider and disk, with high wear performance at the same time. It was found that lubricants with high surface energies suppressed the bouncing of contact sliders. A bouncing height of 3 nm was obtained for a combination of 30% contact sliders and MPBT lubricants. A contact slider design, with a meniscus-controlled contact pad, is proposed for contact sliders using liquid bearing. The bouncing of the slider was suppressed by controlling the etching depth of the meniscus-controlled contact pad, which was larger than the lubricant thickness. High wear performance of the in-contact recording system was confirmed by both the drag test for disks and the seek test for heads.

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We investigated the noise reduction mechanism of a Cr-rich Co₇₂Cr₂₈ perpendicular magnetic recording medium. By increasing the Cr content from 22 at% to 28 at%, the signal-to-noise ratio at a recording density of 70 kFCI was increased from 25 dB to 31 dB. The medium noise was reduced more than the magnetic parameters, such as M_S and H_C⊥. When the average crystalline diameter of the media increases, the medium noise of the Cr 28 at% medium does not increase, whereas that of a Cr 22 at% medium increases. Analysis of a medium with a Ti under-layer shows that the Δθ₅₀ does not have any significant effect on the medium noise. To analyze the noise of these media, we introduced ΔM_⊥ measurement method that takes account of the demagnetization field. The ΔM_⊥ value is related to the medium noise. The relation is different from that of longitudinal medium. Analysis of the minor loops showed that the Cr 28 at% medium has low noise due to its highly stable dc-erased state. MFM observation for 4-μm-wide dc-erased tracks confirmed the mechanism for smaller reversed magnetic domains in a Cr 28 at% medium than in a Cr 22 at% medium. This mechanism contributes to the low noise of the Cr-rich Co-Cr single-layer perpendicular medium.

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The effects of improved background pressure on the deposition of Co-Cr perpendicular anisotropy films were investigated. To obtain a high vacuum, an aluminum alloy chamber was used, whose inside wall was subjected to the EL process ro reduce outgassing from the chamber. The background pressure reached 4×10^-8 Torr after chamber baking. The pressure was changed by the addition of nitrogen to the atmosphere. In spite of the nitrogen addition, the percentage of H₂O in the atmosphere was greater than that of N₂. As a result, we were able to obtain a high perpendicular coercive force and a high crystallinity for the deposition of Co-Cr at a low background pressure. As regards the recording performance, a perpendicular double-layered medium with the Co-Cr recording layer deposited in a high vacuum showed larger output than one deposited in a low vacuum.

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The effects of annealing (1 hour) on the magnetic properties of Co-Cr-M (M=Au, Pt, Nb, Ta) alloy films with Ti underlayers were studied. All the films exhibited an increase in perpendicular coercivity and perpendicular squareness, resulting in high coercivities of more than 2500 Oe and a high perpendicular squareness of 0.6. The saturation magnetization decreased drastically with annealing temperatures above 400°C because of interdiffusion between Co and Ti. An MFM image of a sample annealed at 600°C showed a fine magnetic domain structure.

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Thermal relaxation in perpendicular double-layered media was examined by simulation and experiments, using a single-pole writing head and an MR flying head. A new FEM simulation with a curling switching model is expanded in association with the exponential relaxation theory. The simulation indicates that the relaxation is less at high densities than at low densities. Only a 2% output deterioration due to thermal relaxation was actually confirmed experimentally for about 10⁵ seconds at 5 kFRPI, and there was almost no deterioration at 130 kFRPI. In contrast to longitudinal recording, less output reduction is observed for higher linear densities; this is well explained by the nature of the demagnetization field in perpendicular magnetic recording.

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Co-γ-Fe₂O₃ perpendicular magnetic recording thin-film disks were prepared by annealing a CoO-Fe₃O₄ single layer deposited on an NiO underlayer in air, at temperatures ranging from 260°C to 350°C. The disks had no protective overcoat layers. The noise characteristics of Co-γ-Fe₂O₃ disks were measured by using a MIG-type ring head with a gap length of about 0.2μm in contact sliding use. By measurement of the dc erase noise spectrum and the recording density dependence of the medium noise, it was found that the disks show noise characteristics which is often seen in thin film media. At high recording densities of over 40 kFRPI, the disks show a higher S_p-p/N_m,rms than various longitudinal recording media now on the market.

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Sputter-deposition at high Ar pressures was investigated with the aim of reducing the medium noise of Co/Pd multilayer films for perpendicular magnetic recording media. A large increase in perpendicular coercivity was obtained in samples prepared at Ar pressures above 10 Pa. Angular variations of the coer civity suggested that the magnetization reversal process was dominated by domain wall motion in the samples prepared at Ar pressures below 5 Pa, while it seemed rotational in samples prepared at Ar pressures above 10 Pa. Through recording performance tests with a ring head, it was found that a sample prepared at a high Ar pressure of 70Pa showed a lower medium noise level and higher recording resolution than a sample prepared at 1 Pa.

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Interparticle interactions in a thin-film recording medium affect the recording characteristics and medium noise. The relation between the exchange coupling of particles and the noise in a perpendicular magnetic recording medium was analyzed with a three-dimensional simulation program. The dc-erased medium noise increases significantly with stronger exchange coupling. However, the change in the noise of a high-density recorded medium resulting from a change in the exchange coupling is not as large. In addition, the exchange coupling increases the playback voltage, because it helps to align the direction of magnetization in the recorded bit area. As a result, the exchange coupling increases the signal-to-noise ratio.

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Although there have been many attempts to use high-sensitivity magneto-resistive (MR) heads in perpendicular magnetic recording, their readback resolution not high enough, because of their large shield gap length. are We describe MR head that has a high D₅₀ of 270 kFRPI with a narrow shield gap associated with a differential equalizer, The S/N ratio of the equalized signal is also investigated.

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A low-flying type of magnetic recording head is necessary for optimum performance in perpendicular magnetic recording (PMR), because PMR is more sensitive to spacing loss than longitudinal magnetic recording. We developed a thin-film magnetic recording head for PMR by combining a single-pole head and a low-flying slider with a flying height of 25 nm at a disk velocity of 10 m/s. In this paper, the effects of the head and medium parameters on the read/ write performance of a single-pole head with double-layered media are discussed, and the write characteristics of the single-pole head in the high-frequency region are investigated on the basis of the O/W performance and the recorded bit images observed by MFM.

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To investigate the possibility of a magnetization-buckling mode in a perpendicular magnetic film with columnar structure, the magnetic energy of the film is calcu lated on the assumption that the film is a two-dimensional array of single-domain prisms. From the energy, the nucleation field H_N is calculated and compared with H_N for the magnetization-curling and coherent-rotation modes. It is found that the magnetization rotates in the coherent-rotation mode for a small reduced-radius S and in the curling mode for a large S. The buckling mode occurs in the range of S between the ranges for the coherent-rotation and curling modes. However, the range of S in which the buckling mode occurs is very small or non-existent when the space between the crystallites and the axial ratio of the crystallite constituting the film are small. Moreover, H_N in the buckling mode is very close to H_N in the coherent-rotation mode. Therefore the buckling mode need not be taken into account in perpendicular magnetic films with columnar structure.

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The potential advantages of magnetically induced super-resolution (MSR) for high-density recording in magneto-optical disks have spurred the study of various related technology. MSR systems can read signals from a smaller area than the laser spot area by using magnetic films with different temperature characteristics. Most MSR systems require an external magnetic field in the readout. We have developed a new type of MSR (S-RAD) that does not require an external magnetic filed. The front masking area of the S-RAD is formed by shrinking the recording mark in the readout layer. This paper describes the readout principle and readout characteristics of S-RAD. A C/N of 49 dB was obtained at the 0.5μm recording mark. A crosstalk level of less than -40 dB was obtained at a track pitch of 0.8μm. We believe that S-RAD has sufficient potential to allow practical use of high-density magneto-optical recording.

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We developed a magnetic-super-resolution overwritable magneto-optical medium. It be arranged an enhanced structure, because a readout layer and overwritable layers are coupled magnetostatically.
Direct overwriting is done by light intensity modulation, and readout uses the magnetic-super-resolution method. When the length of a recording mark is short, the carrier-to-noise-ratio is high and the erasability is low in comparison with those of a conventional medium.

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Magnetically induced super-resolution (MSR) by rear aperture detection (RAD) is characterized by very low cross-talk and very high resolution due to the use of both front and rear masks within laser spot. We investigated the possibility of making high-density Magneto-optical disks that use RAD combined with land-groove recording with a 690-nm wavelength diode laser and a 0.55 NA objective lens. We achieved a bottom jitter of 8.4% in grooves and 9.5% on lands, and a recording power margin of ±16.5% in grooves and±15.5% on lands at an areal density of 3.69 Gbit/in², with a 0.70-μm track pitch and a 0.25-μm bit length. These obtained values are acceptable for a magneto-optical disk system with a capacity of 5 GB/120 mm or 2 GB/8 mm.

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We studied the magnetic field sensitivity in a double layer which was composed of a TbFeCo recording layer with low Tb content and a high-T_c RE-rich DyFeCo ultrathin layer. The Tb₁₄Fe₈₂Co₄/Dy₃₀Fe₃₅Co₃₅ double layer has better magnetic field sensitivity than a TbFeCo single recording layer. We concluded that the high C/N of the double layer disk was caused by the large M_S of the recording layer and suppression of micro-domain nucleation by the ultra-thin DyFeCo layer.

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Tri-layered films composed of magnetic garnet Bi, Ge, Co: DyIG, highly Ga-substituted Bi: DyIG, and Bi, Ga: DyIG layers were deposited by the laser ablation method, and their magneto-optical properties were investigated. The Faraday rotation of the Bi, Ge, Co: DyIG, and Bi, Ga: DyIG layers showed opposite signs in the short-wavelength region from 0.45μm to 0.7μm. The magnetic moment of the Bi, Ge, Co-and Bi, Ga-DyIG layers independently switched in the presence of an external magnetic field. We proposed that the Bi, Ge, Co, and Bi, Ga substituted DyIG films are promising materials for wavelength multiplexing optical memory.

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Surface damage and magnetic structures in laser-annealed magnetic garnet films investigated by the use of scanning probe microscopes, were i.e., Atomic Force Microscope (AFM), Magnetic Force Microscope (MFM), and Near-field Scanning Optical Microscope (NSOM). AFM images showed the atomically flat surface of the laser-annealed region in which the growth-induced magnetic anisotropy was strongly reduced. MFM and NSOM images showed sharp changes in the direction of magnetization at the boundary between the laser-annealed region and laser-annealed region. These results show that the laser-annealing technique is very useful for fabricating waveguide optical isolators.

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MnSbPt films containing 50 at%Mn, 44 at%Sb, and 6 at% Pt were prepared by RF sputtering. XRD, TEM, and NMR studies revealed that in the as-deposited state, MnSbPt films had a disordered hexagonal structure, and that after annealing at 300°C NiAs-type structure and an fee-type structure were formed, promoting phase separation in MnSbPt films with a giant magneto-optical Kerr rotation. The assumption of a two-phase mixture of NiAs and fee structures is difficult to explain the giant magneto-optical effect in the short wevelength region (∼500 nm) for MnSbPt films. The giant magneto-optical effect is thought to be associated with the microstructure due to the phase separation process.

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MnSb films prepared on GaAs(100) and (111)B substrates by atomic-were hydrogen-assisted hot-wall epitaxy technique. Atomic-force microscopy observation revealed a drastic improvement in the surface flatness of MnSb films grown with irradiation of atomic hydrogen. X-ray diffraction showed that the growth surface of MnSb films was (10.1) in those grown on GaAs(100) substrates, and (00.1) in those grown on GaAs(111)B substrates. The spectra of the optical reflectivity and the polar magneto-optical Kerr effect were measured in the films obtained and analyzed in terms of the electric conductivity tensor.

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Ferromagnetic MnAs thin films were grown on GaAs(100) and (111)B substrates by the atomic-hydrogen-assisted hot-wall epitaxy technique, using polycrystalline powder of MnAs as evaporation source. The source and substrate temperatures were 700°C and 400°C, respectively. The surface orientations of the MnAs films grown on (100) GaAs substrates (1011) and (1012), (111)B GaAs was (0001). The polar magneto-optical Kerr rotation and ellipticity spectra and reflectivity spectrum were measured in the films. The dielectric permeability spectra were calculated from experimental data, from which the magneto-optical spectra were analyzed.

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Magneto-optical polar Kerr effects between 1.5 and 6 eV and the domain structures of body-centered cubic (bcc) FeRh alloy, bcc FeRh_0.82Pd _0.18 alloy, and body-centered tetragonal (bet) FeRh_0.24Pt_0.76 alloy were investigated for the first time. A temperature-induced AF-FM phase transition was attained at a temperature width of 2 K for FeRh and FeRh_0.82Pd_0.18 alloys at a temperature width of 40 K for FeRh_0.24Pt_0.76. A large width of the transition for FeRh_0.24Pt _0.76 was also observed in the temperature dependence of domain structures investigated by magnetic force microscopy, and may be attributed to the internal stress caused by the anisotropic change in the lattice constants during the transition. The Kerr rotation spectrum of FeRh showed two negative peaks near 2.8 eV and 3.8 eV, which may be due to the contribution of Rh. In the spectrum of Pd-doped FeRh_0.82Pd _0.18, a new peak appeared around 4.8 eV and enhanced the rotation. The spectrum of FeRh_0.24Pt_0.76 alloy resembles that of FePt alloy, and no contribution of Rh is observed.

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Multilayers of Ti/Fe/[Nd−Fe−B/Fe]×5/Ti/glass whose Fe layers had thicknesses ranging from 0 to 50 nm and whose Nd−Fe−B layers had thicknesses ranging from 0 to 100 nm were fabricated by RF sputtering. Magnetization measurements showed that the minor loops of almost all the multilayers exhibited spring−back behavior, which suggests exchange−coupling between the Fe and Nd−Fe−B layers. To estimate the coupling strength between the Fe and Nd−Fe−B layers, we performed a micromagnetic calculation of the magnetization curves. From a comparison of the experimental and calculated results, we can infer that the coupling strength between Fe and Nd−Fe−B layers is about 2.0×10 ^{− 3} J/m², which is about 10% of that in Fe/Fe and Nd−Fe−B/Nd−Fe−B couplings.

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Nanocrystalline bulk Fe₈₈Nb₂Nd₅B₅ and Fe₈₆Nb₂Nd₇B₅ alloys were made by consolidating amorphous powders with a spark-plasma-sintering method and subsequent annealing. Bulk alloy made by consolidating amorphous powders has a higher density than that made by consolidating crystalline powders, presumably because the amorphous alloy softens around the crystalline temperature. Bulk Fe₈₈Nb₂Nd₅B₅ and Fe₈₆Nb₂Nd₇B₅ alloys made by consolidating amorphous powders at a temperature of 873 K and a pressure of 636 MPa have a density of 7.5 g/cm³, and form a nanocrystalline composite structure of bcc-Fe, Fe₃B, and Nd₂Fe₁₄B phases with grain sizes of 20-40 nm after annealing at 1023K. Nanocrystalline bulk alloys show hard magnetic properties, remanence (J_r) of 0.83-1.0 T, coercive force (H_cJ) of 190-290 kA/m, and maximum energy product (BH)_max of 43-49 kJ/m³.

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Melt-spun ribbons of Nd-Fe-Co-Cu-Nb-B system alloys were prepared by the single-roller rapid-quenching method, and the effects of the composition, wheel velocity, and heat treatment on the magnetic properties were investigated. The optimum preparation conditions and some properties are as follows: composition, Nd₅Fe₇₁Co₅Cu_0.5Nb₁B_17.5; wheel velocity, 20 m/s; annealing conditions, 650°C ×10min in Ar atmosphere; magnetic propeties, J_r = 1.175 T, H_cJ = 342.6 kA / m, H_cB = 307.6 kA / m, (BH)_max=1 14.8 kJ/ m³, α(B_r) = -0.056%/°C, β(H_cJ) = -0.354%/°C.

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The dependence of the magnetic properties on the nanostructures of (Sm, Zr)Fe₇N_x+α-Fe composite magnets have been investigated. As-quenched sample consists of TbCu₇ type Sm-Fe phase (SmFe₇ phase), amorphous phase and a-Fe phase. After heat treatment at 550°C for 1 h, amorphous phase turned into SmFe₇ phase mainly. After nitrogenation, magnetic properties changed drastically with crystallization heat treatment temperature. These changes must be caused by phase transformations rather than change of nanostructures. Peak (BH)_max value could be obtained by heat treatment at 700-800°C which are higher than crystallization temperature.

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Application of a hard magnetic alloy, Fe-39.5%Pt-0.75% Nb, to dental parts such as crowns and bridges, was investigated. The material has excellent magnetic properties and corrosion resistance. All of the samples were produced by the dental casting method, and the optimum conditions for producing good hard magnets for crowns and bridges were determined. The results obtained were as follows: Casting by means of alumina and magnesia investment showed good results as regards the surface roughness of alloys. The alloys made by dental casting showed energy products as high as 15 MGOe. The attractive force was in the range from 600 to 700 gf, which is required in applications for removable dental parts.

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Magnetization measurements in steady fields of up to 300 kOe were performed for disordered and ordered Ni_1-xMn_x alloys prepared by rapid quenching and subsequent annealing, in order to study the correlation between atomic ordering and magnetic properties. The high-field susceptibility of the rapid-quenched samples exhibited a maximum near x = 0.25, while that for the annealed samples had a distinct minimum also near x = 0.25. Magnetization isotherms at 4.2 K for rapid-quenched samples with 0.19≤ x ≤0.34 revealed the existence of considerable hysteresis, suggesting the existence of spin-glass-like states. The temperature dependence of low-field magnetization for the same samples exhibited typical freezing behavior at low temperatures, namely, an irreversibility of field-cooled and zero-field-cooled magnetization. The freezing temperature was found to increase with increasing Mn content x.

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Polycrystalline samples of the layered perovskite La_2-2xCa_1+2xMn₂O₇ with quasi-two-dimensional Mn-O networks were synthesized, and a magnetic phase diagram obtained. La_2-2xCa_1+2xMn₂O₇ has a two-type spin exchange interaction, one of which reflects the properties of the a-b plane, and the other properties of the c axis (out-of-plane) direction. As a result, for 0.22≤x≤0.5, there are three regions: PI (paramagnetic insulator), F1 (ferromagnetic insulator), and FM (ferromagnetic metal). We observed a giant magnetoresistance (GMR) of Δρ/ρ₀=64% (77 K, 1.8T, x=0.25), which is much larger than that reported for the three-dimensional perovskite La_1-xCa_xMnO₃. These results could be interpreted as due to anisotropic exchange interactions of La_2-2xCa₁+_2xMn₂O₇.

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In copper iron oxide (CuFe₂O₄: Cu-ferrite), two-fold degeneracy of the dγ level of the Cu²⁺ ions on the octahedral site which is the Jahn-Teller center is lifted owing to the Jahn-Teller distortion below 360°C and has the degeneracy above 360°C To investigte the dγ level, the valence band of Cu-ferrite was analyzed by means of X-ray photoelectron spectroscopy (XPS). The dγ signal of XPS appeared at a shoulder on the low-energy side in the 3d orbital below 360°C and disappeared above 360°C From the width of the dγ signal, the Jahn-Teller energy was estimated to be about 0.3-0.4 eV. The properties of the magnetization and electric conductivity of Cu-ferrite changed according to the state of the dγ level.

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A new III-V based diluted magnetic semiconductor, GaMnAs has been successfully grown on (001) GaAs using low-temperature molecular beam epitaxy. The GaMnAs films have p-type conduction with hole concentrations ranging from mid 10¹⁷ to low 10²⁰ cm^-3, exhibiting ferromagnetic ordering at low temperatures. Magnetic and magnetotransport properties are studied at low temperature.

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The viscous force acting on the magnetic flux in a high-T_c Bi₂Sr₂Ca₂Cu₃O₁₀ superconductor was evaluated by applying a pulsed magnetic field. It was found that the magnetic flux intruding into the superconductor moves at a speed of about 50 m/s. The viscous force and the pinning force in a Bi-based high-T_c superconductor are discussed in the framework of the critical state model. The viscosity (η/φ₀) of the magnetic flux was estimated to be about 1×10⁵A·s/m³.

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The martensitic structure and magnetic domain structure of Fe_1-xNi_x system (0.30≤x≤0.32) were investigated by means of non-contact atomic force microscopy and magnetic force microscopy. The martensite has a stripe domain structure whose period decreases with the Ni composition. The magnetic anisotropy constant in the martensite was estimated to be 2×10⁴ J/m³, whose magnitude is the same order as that of Fe or Ni metal.

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In this study, we investigated the effects of strong magnetic fields of up to 14 T on the thermal agitation of water and ethanol. We measured the Raman spectrum and Rayleigh scattering of water-ethanol system. The Raman spectra of water-ethanol system in the range of 450-700 nm were not affected by 8 T magnetic field. However, the Rayleigh scattering intensity decreased significantly during 8 T magnetic field exposures. We also investigated the near-infrared spectrum of water. The peak wavelength shifted from 1930 nm to 1932-1933 nm under a 14 T magnetic field. There is a possibility that the formation of hydrogen bonds is enhanced and the thermal agitation of water molecules decreased under strong magnetic fields of up to 14 T.

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