The recording field of a narrow-track, single-pole (SPT) write head was investigated using three-dimensional eddy-current transient finite element analysis. Finite element model for this SPT head with a double-layered medium was examined and it was found that the area of the medium was a key factor to reduce computation time while maintaining sufficient accuracy of the solution. The calculated head field exhibited large peak field and followed the 0.5 - 2 GHz drive current closely. This fast response answered to the concern about a slow response caused by eddy currents in the thick metallic under-layer. Finally, we discussed the capability of the SPT head for high areal-density recording.

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In order to reduce medium noise in Co/Pd multilayer perpendicular media, we applied a granular seedlayer, such as Au-SiO₂, and added B and O into the magnetic layer. Using a ring-shape recording head and a perpendicular medium with no soft magnetic under layer, we obtained good overwrite and low noise.

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The effect of thermal agitation of magnetization on the magnetic properties of CoCr-based perpendicular recording media was studied using a pulse magnetometer. In media having well-segregated grains, we found that the angular dependence of the “intrinsic” remanence coercivity H₀, obtained by subtracting the thermal agitation of magnetization, was nearly the same as that of coherent switching of magnetization calculated by taking account of the angular distribution of the preferred axis. Experimental and theoretical analyses suggested that the achievable maximum value of the ratio of H₀ to the anisotropy field H_k is 0.7 to 0.8 at 20-nm thickness. Results show that the value of perpendicular anisotropy K_u must be more than 3 times larger than 2πM_s² values in order to achieve an M_r/M_s of nearly 1.0 resisting the thermal agitation effect in CoCr-based perpendicular media.

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Pt/Ti layers were investigated for the under layers of Co-Cr-Ta perpendicular magnetic recording media. The Co-Cr-Ta/Pt/Ti trilayered films exhibited better c-axis orientation and higher perpendicular coercivity than the Co-Cr-Ta/Pt bilayered films. In order to decrease grain size of the Co-Cr-Ta recording layer, a 5-nm-thick Pt interlayer was introduced to compose [Co-Cr-Ta/Pt]_n multilayers. We found that the Pt interlayer was effective for decreasing the grain size of the Co-Cr-Ta recording layer without degrading its perpendicular coercivity. The Pt/Ti under layer and Pt interlayer are useful for the development of Co-Cr-Ta perpendicular magnetic recording media.

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Magnetoplumbite-type BaM ferrite films deposited on Pt under layers have a large perpendicular anisotropy which is enough for the contact type of perpendicular magnetic recording media. Addition of Ta proved thoroughly effective in attaining smaller grain size in BaM ferrite films. By adding 1 at.% of Ta into Pt under layers, we decreased the grain size of those Pt under layers. BaM ferrite films with smaller grain size have higher perpendicular coercivity (3.5 kOe) and greater squareness (0.69). Lower noise level and higher recording density were obtained through this improvement.

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We investigated the dependence of media noise on the writing head in perpendicular magnetic recording. Transition noise modeling, discussed first, provided measurements for various write heads to determine head field influence. Results show that transition jitter corresponding to medium noise correlates with the head field gradient. Sharpening head field gradient is thus an efficient method for reducing the medium noise.

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Because single-pole heads used with perpendicular recording media have a very sharp head field distribution, high-resolution bit writing can be obtained. Indeed, using a flying height of around 50 nm, an erase-band width of around 30 nm has been measured. Low track-edge noise is also very important to the overall performance of the system, however. In this paper we discuss simulated head field distributions and track-edge noise performance through measurement of off-track noise profiles, obtained using a spin-stand. For a single-pole write head with perpendicular double-layer media, almost no track-edge noise was observed.

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CoCrPt single-crystal thin films were prepared on single-crystal substrates of Al₂O₃, LaAlO₃, and SrTiO₃. A good single-crystal of c-axis-oriented CoCr₁₉Pt₁₀ thin film was obtained on an Al₂O₃(0001) substrate when CoCr₁₉Pt₁₀ film was deposited via a non-magnetic CoCr₂₅Ru₂₅ under layer. Structural analyses were carried out by X-ray diffraction and transmission electron microscopy. The epitaxial relationships between the magnetic layer and the substrate were determined for various oxide substrates. Results demonstate that the substrate and the non-magnetic under layer play important roles for growth of a CoCrPt single-crystal thin film with good crystallographic quality.

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Perpendicular magnetic recording is expected to be a prominent candidate for ultra-high-density recording at more than 100 Gb/in². We have developed an analytical method for estimating the read/write performance and thermal decay characteristics. This report focuses discussion on the analysis of low-frequency relaxation process such as hysteresis loops and magnetization decay. The magnetization reversal induced by thermal energy was calculated using Neel-Arrhenius-type model. The calculation conditions which reproduced a practical hysteresis loop could predict the thermal decay characteristics of the written pattern. The accuracy of this estimation is verified by the data from a 52.5 Gb/in² demonstration, and the specifications for an areal recording density of 100 Gb/in² is proposed based on this analysis.

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To study the behavior of magnetization at the beginning of magnetization reversal in a perpendicular magnetic film, we calculated the nucleation field H_N as a function of the magnetocrystalline anisotropy constant K, the exchange constant C, and the deviation of easy axis from the z-axis ω. It was found that a grain with an inclined easy axis jumps at smaller H_N and then enhances the magnetization jump in the surrounding grains if C is not too small. If C is very small, however, the reversed magnetization prevents the magnetization in the surrounding grains from jumping.

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A method using MFM was investigated for analyzing the magnetization state of CoCrPtTa perpendicular magnetic recording media. Adequate resolution to determine the magnetic cluster size was obtained at a sample-tip spacing of less than 50 nm. The magnetic cluster size obtained in MFM analysis corresponded to the experimental value obtained using an MR head. Ratio of white to black area in dc erased state however, seems to have little correlation with squareness obtained from M-H loop. Time dependence of MFM images revealed the occurrence of thermal decay of the magnetic cluster. Hence it is necessary to take the thermal stability of the magnetic cluster into account in analysis for perpendicular magnetic recording media.

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Sputter-deposited amorphous carbon was applied as an under layer of Co/Pd multilayer perpendicular magnetic recording media. As the C under layer thickness increased, the perpendicular coercivity H_c and the nucleation field -H_n values increased, whereas the α (= 4π (dM/dH)_H=Hc) value decreased. The conspicuous decrement of magnetic domain size with increasing C under layer thickness was observed by MFM analysis. In the read-write characteristic, an increase in the reproduced output and a reduction of the medium noise were both obtained in media that showed a high H_c, a high -H_n, and a small α. Results showed that a thicker C under layer enabled the Co/Pd multilayer to accomplish weak magnetic exchange interaction, which leads to high H_c and S/N values.

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The effect of the medium backlayer thickness on write performance was investigated using a single-pole head with a narrow track width. It has been reported that the product of B_s and thickness of the medium backlayer must be larger than 1/6 of that of the head main pole for large track widths. Good recording performance was confirmed with a track width as narrow as 0.26 μm while the above condition was satisfied. This means that the above condition is sufficient even for a 0.26-μm-wide track head. Furthermore, results showed a possibility that the product of B_s and thickness of the medium backlayer was reduced in narrow track-width recording.

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We proposed a new analysis using perpendicular torquemetry to evaluate the thickness of the initial growth layer, and to define the intrinsic magnetocrystalline anisotropy of columnar structure. In CoNiCrTa media, the initial growth layer consists of nano-crystalline grains whose c-axes are randomly oriented in three dimensions, and the columnar structure consists of grains with the c-plane parallel to the film plane. The plotted product of perpendicular anisotropy to magnetic film thickness versus magnetic film thickness (K_u^⊥ × d_mag. vs d_mag.) for these media reveals that magnetic grains in the columnar structure have a constant uniaxial magnetocrystalline anisotropy of the order of 10⁶ erg/cm³, independent of the magnetic film thickness. By taking account of magneto-optical analysis, we can derive the magnetization process of the initial layer, which is mutually coupled with the neighboring columnar structure, due to its soft magnetic property.

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Heterogeneity of the perpendicular magnetization process dependence on film depth for CoNiCrTa and CoCrTaPt perpendicular thin-film media is discussed based on a magneto-optical analysis. Results show that: (1) by means of longitudinal Kerr equipment, evaluation for separating longitudinal magnetization of a columnar structure and initial layer is possible; (2) in a perpendicular magnetization process, the top of the medium has high coercive force and high squareness compared with the bottom of the medium; and (3) the top of the medium has homogeneous magnetization thicker than 25 nm, and the bottom has a thickness of about 10 nm. The top and bottom of the medium are considered to be a columnar structure and initial layer, respectively.

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The recording characteristics of perpendicular media with a ring head were investigated experimentally and by simulation to determine their suitability for high-density perpendicular recording. The recording mechanisms of both perpendicular single-layered and double-layered media were clarified by MFM analysis and simulation of the recorded magnetization pattern with a head skew angle. It was found that the effect of the head skew angle on the recording characteristics differs between single-layered and double-layered media.

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Dependence of a recorded magnetization pattern, using a ring head for both single-layered and double-layered perpendicular media, on the magnitude of the magnetomotive force was investigated by computer simulation. It was found that the magnetization pattern of the single-layered medium with a large recording current became indistinct because of both a decrease in head field gradient and an increase in transition curvature. The magnetization pattern of the double-layered medium, however, was distinct at a large recording current.

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It is very useful to evaluate the magnetization vector in extremely thin films by combining the results determined by Hall voltage measurement and those observed by the conventional VSM method. Major and minor loops of a 30-nm-thick Co-Cr-Ta single layer implied that a magnetization reversal occurs mainly in the in-plane direction at a relatively low magnetic field. On the other hand, a 30-nm-thick Co-Cr-Ta film deposited on a (111) plane-oriented Pt underlayer revealed a more definite c-axis orientation than the Co-Cr-Ta single layer. Magnetization reversal of Co-Cr-Ta/Pt film occurs mainly in a direction perpendicular to the film, in spite of its large perpendicular anisotropy.

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A self-consistent read/write simulation based on a finite element method of the Maxwell equations was performed on a two-dimensional model of a system consisting of a keepered medium (KM) with a thin soft magnetic layer (keeper layer) over a recording layer and a thin-film head. The M-H hysteresis model used is a modified Stoner-Wohlfarth model, in which the temperature-dependent switching of single-domain particles is taken into account by the Monte Carlo method.
We confirmed that thermal stability is greatly improved in the KM. The enhanced stability is caused by reduction of the demagnetizing field in the transition area as well as the bit center of the recorded magnetization.

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In order to apply a thin-film medium with a high-density magnetic recording capability to organic substrates for a magnetic tape or flexible disk, reduction of preparation temperature is the key technology. We found that an Ru under layer is effective to increase coercivity for Co-Pt-based thin films at low preparation temperature. Increasing the Ru under layer thickness and Pt composition of the magnetic layer increases coercivity. Addition of boron and oxygen to the magnetic layer is effective to reduce medium noise. With addition of boron and oxygen, Co-Pt grains are separated magnetically by a B-O non-magnetic boundary.

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In this study, the dependence of the magnetic properties of Sm-Co layers prepared on the Cr underlayers on Sm concentration, sputtering pressure, and power were studied to increase the coercivity of the film and to apply the film to high-density recording media. The film with a coercivity of about 4.5 kOe was prepared by adjusting the conditions. It was confirmed by the analysis of the selected area electron diffraction pattern that the crystal structure in Sm-Co film consists of a mixture of crystallites and amorphous matrix. The D₅₀ of Sm-Co/Cr disk was about 130 kFRPI.

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The macroscopic in-plane magnetic anisotropy induced in Co-alloy thin-film media deposited on textured substrates, arises mainly from the orientation of easy magnetization axis of the Co-alloy in the circumferential direction. This anisotropy correlates with in-plane distortion of the crystal structure of the Cr under layer. Correlation between the substrate surface microstructure and distortion of the Cr crystal structure was investigated as an effect of anisotropic stress caused by the thermal expansion of substrates. We found that the Cr crystal structure becomes distorted, and a large magnetic anisotropy is induced, when the grain size is less than half the width of texture grooves. In this case, the different thermal expansion coefficients of NiP and Al make the thermal strain of the inclined plane of texture grooves larger in the circumferential direction than in the radial slope direction. The stress on Cr grains from the substrate surface therefore becomes anisotropic and induces distortion of the Cr crystal structure. The anisotropic stress also correlates with the in-plane magnetic anisotropy.

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Sputter-deposited Si was applied as an intermediate layer of a perpendicular/longitudinal composite medium. In the case of the composite media with a carbon intermediate layer, a paramagnetic Co-Cr film with a 20 nm thickness was necessary for inhibiting diffusion of the C atoms into the magnetic layer. AES analysis revealed that Si atoms diffuse very little into the longitudinal and perpendicular magnetic layers, which means that the extra intermediate layer is unnecessary. Accordingly, intermediate layer thickness was reduced to 5 nm by applying Si.
In a read/write experiment, the composite medium exhibited a higher reproduced voltage than the perpendicular single-layered medium up to 400 kFRPI, which is attributed to the thin intermediate layer. Moreover, it was found that the composite medium has better thermal stability than the single-layered medium at a recording density of 2 kFRPI.

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The microstructures of Co₇₃Cr₁₈Pt₆Ta₃/Ni₉₅Cr₅ and Co₇₃Cr₁₈Pt₆Ta₃/Ni₉₅Cr₅/Ti media were investigated in the direction parallel to the film thickness. The Co₇₃Cr₁₈Pt₆Ta₃/Ni₉₅Cr₅ media showed higher perpendicular coercivity, by about 1000 Oe, than that of Co₇₃Cr₁₈Pt₆Ta₃/Ni₉₅Cr₅/Ti media for thicknesses of more than 50 nm of the CoCrPtTa layer. Results showed that a Ti under layer enhances the preferred orientation of Co(001), which causes increased diameters of grains and magnetic clusters. We consider the difference in size of grains and magnetic clusters of these media to affect their magnetic and noise properties. An under layer that achieves more precise control of both preferred orientation and grain size is required for under layers of perpendicular magnetic recording media.

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To reduce grain size while maintaining high coercive force in longitudinal thin-film media, we applied a combination of deposition of a very thin WCr seedlayer with a dry-etching process to a magnetic medium material with comparatively high magnetocrystalline anisotropy. As a result: (a) the deposition of a 0.5-nm WCr seedlayer reduced the grain size from 9.1 nm to 7.9 nm; (b) the SN ratio of the medium with 0.25-nm − 1.0-nm-thick WCr seedlayer increased by 1.5 dB due to a 20% decrease in medium noise compared with the standard medium without WCr seedlayer, caused mainly by reduction of the grain size; and (c) in the case of media with WCr seedlayer thickness less than 1.5 nm, high coercivity was maintained due to strong c-axis orientation and high thermal stability (ν_actK_u^grain/k_BT > 80), enabling these media to maintain a high recording resolution. Consequently, application of this sputtering process to media with high magnetocrystalline anisotropy stability is very effective in improving SN ratio while maintaining recording resolution.

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This paper describes two methods of making narrow photoresist frame patterns to fabricate the top pole of writing elements. First, a KrF excimer laser stepper was used to expose a thick photoresist for fabrication of top poles. Second, the tri-layer resist frame method using reactive ion etching (RIE) was examined for fabricating the resist frame. Thick photoresist could be resolved by the KrF excimer laser stepper. Furthermore, the off-axis (annular) illumination exposure method could increase the depth of focus. By using Ta hard mask layer for the tri-layer resist frame method, we were able to make a 0.25-μm wide frame.

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A new head design for a single-pole head is proposed. The head is driven with pancake-structure dual coils, which sandwich a main pole and excite a main-pole tip effectively. High recording sensitivity was achieved in comparison with a conventional single-pole head. Furthermore, since the main pole is sandwiched between two return-path yokes, which act as a magnetic shields, a high robustness with regard to external stray fields was confirmed, up to at least an external field of 20 Oe.

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The state of recorded magnetization and reproduced wave form of a metal evaporated tape with high anisotropy were investigated for the case in which the magnetic field direction of the recording head tilted from the normal plane which contained the easy axis of the tape. When the direction of recorded track tilts from the normal plane which contains the easy axis, magnetic charges appear at the track edge because the magnetization has a strong tendency to turn to the easy axis direction. These magnetic charges affect the reproduced waveform; the difference was observed between the reproduced waveforms from both track edges.

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A magnetic contact duplication technique using a lithographically patterned master medium was investigated in order to write a servo signal on hard disks and floppy disks at high speed and low cost. In this technique, the coercivity of the master medium is low, and a dc magnetic field is applied to a slave medium in contact with the master medium. Experimental and computer simulation results show that the degree of magnetic duplication becomes better and then saturates as the magnetic layer thickness of the master becomes thicker. Magnetic duplication performance improves with the increase of M_s of the master.

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A two-step computer simulation using a two-dimensional finite element method was devised in order to handle the magnetic properties in high frequencies. The dynamic impedance variation rate of the high-carrier-frequency magnetic head, which corresponded to AM percentage modulation, was also proposed in order to estimate the reproduced output level of the head. The model of reproducing signal magnetization on a magnetic recording medium using a ring-type magnetic head, which included the high-carrier-frequency sensor in part of the magnetic path, was calculated by the two-step computer simulation method. Large dynamic impedance variation rates of 10 to 28 % were obtained in reproducing the signal magnetization of the 0.1- to 2.0-μm record wavelength. This indicated the possibility of a high-carrier-frequency magnetic head for 100 Gbits/in².

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We studied the read/write characteristics of a high-density longitudinal recording system at more than 40 Gb/in². For accurate design of a recording system with high track density, we introduced noise/signal ratio by unit read track width as a parameter. This method was employed in the design of a 40 Gb/in² recording system.
Based on the design parameters, we fabricated CoCrPtX media with a layer structure optimized for low noise and thermal stability. A narrow shield Spin-Valve (SV) GMR head was also fabricated to achieve high linear recording density. System tests registered a density of 39.8 Gb/in².
After, we improved the media and the head, 53 Gb/in² was demonstrated.

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We successfully fabricated a multilayer structure consisting of a semiconductor-magnetic hybrid material GaAs:MnAs and GaAs / AlAs distributed Bragg reflectors, which is a one-dimensional semiconductor-based magneto-photonic crystal. Significant enhancement of magneto-optical effect was demonstrated around 980 nm at room temperature and under a relatively low field of 0.1-0.2 T. Magneto-optical spectra of this multilayer system were well explained by theoretical calculations. The mechanism for enhancement of magneto-optical effect and the conditions required for application to optical isolators are discussed. Some approaches toward higher magneto-optical performance were investigated. Since our material system is composed of all semiconductor-based materials, our results potentially lead to a new class of magneto-optical devices integrated with III-V based optoelectronics.

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We calculated the x-ray absorption (XA) spectra and magnetic circular dichroism (MCD) spectra of nonmagnetic elements in ferromagnetic orderd alloys (Pd 3p in Pd₃Fe, Sb 3d in NiMnSb, and S 2p in CoS₂) by the first-principles LMTO-ASA method in the framework of local spin density approximation (LSDA). The calculated spectra for Pd₃Fe and NiMnSb are in good agreement with experimental results. The origin of the large satellite peaks of Pd 3p XA spectrum in Pd₃Fe was found to be the transition from core 3p state to s-d hybridized band states above the Fermi level. The calculated results of XA and MCD spectra for CoS₂ were not satisfactory as the calculated Kerr spectra. The reason seems to be the deficient description of band states by LSDA due to its strong electronic correlation effects.

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Rear Expansion Detection (RED) magneto-optical media with different intermediate layers were studied to investigate the mechanism of domain expansion readout. A TM-rich GdFe-M intermediate layer was found to improve the readout margin. A domain written with light intensity modulation (LIM) expands with the wall energy gradient as a driving force under a readout field, compensating for the shrinkage force of an expanding domain. After the expansion, the expanded domain shrinks through wall motion toward the high temperature region with the wall energy gradient as a shrinking force. The above intermediate layer reduces friction during wall motion by reducing both wall coercivity and the demagnetizing field. Domains written with laser pulse magnetic field modulation (LP-MFM) were found to expand with a zero field if the groove wall angle of the substrate is sufficiently high. At mark length of less than 0.3 μm, the shape of marks written with LP-MFM are more suitable for RED.

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Characteristics of new MAMMOS (Magnetic AMplifying Magneto-Optical System) were evaluated. This method needs only a dc magnetic field for expanding the magnetic domains. We obtained 43 dB of CNR for 0.25 μm packed domains by applying 10 kA/m of dc magnetic field. Compared with the conventional CAD (Center Aperture Detection) disk, the CNR for domains smaller than 0.4 μm was greatly improved.

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The magnetic properties of (Co_100-xFe_x)₅₀Pt₅₀ (0 ≤ x ≤ 100) alloy thin films in conjunction with the structure are studied. The intrinsic perpendicular magnetic anisotropy constant K_u measured at room temperature increases with order parameter S and decreases with tetragonality c/a. This result is at variance with a calculation based on first-principle analysis at the order parameter S=1. K_u increases with S for all compositions. The estimated K_u values obtained by extrapolation to S=1 for (Co_100-xFe_x)₅₀Pt₅₀ would be nearly the same for x from 0 to 56, but increases with x for x larger than 56. The present result is consistent with the theoretical one, provided that the temperature dependence of K_u is neglected.

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Thin-film magnets, composed of nanophase dispersed Nd₂Fe₁₄B and α-Fe, were synthesized by rf magnetron sputtering onto glass substrates in an Ar atmosphere. Magnetization curves for films with different α-Fe volume fractions (V_Fe) were single-phase-like, suggesting a firm exchange coupling between hard and soft phases. With increasing V_Fe, the saturation magnetization increased linearly, while the coercivity decreased. Ferromagnetic resonance measurements were made by using a high-frequency, high-field ESR apparatus, which exhibited two absorption peaks when the field was swept with a fixed frequency. A model calculation of the resonance field was made for a simplified hard/soft two-sublattice system to analyze these results. Estimated values of the exchange-coupling constant are in good agreement with those estimated from micromagnetic analysis of the magnetization curves.

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Densification of exchange-spring magnet ribbons of Nd_xFe_85-xCo₈V₁B₆ (x = 7 to 11) alloys was investigated. The ribbons were compacted by a spark-plasma sintering method. The bulk magnets, consisting of multiple phases of the Nd₂Fe₁₄B type and the α-Fe type, exhibited a spring-back phenomenon and had magnetically isotropic properties. With decreasing Nd content, B_r increased and H_cJ decreased. Optimum Nd content was 10 at.%, for which the highest energy density of 134 kJ/m³ and density of 7.76 × 10³ Mg/m³ were obtained.

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Magnets prepared from Nd-Fe-B based melt-spun powder, using a powder compacting press, have not been applied to thin arc-shaped magnets for small magnet motors up to now. We developed new techniques to prepare a granular compound with epoxy resin binder and to press it into arc-shaped segments with Ti- and C-ion-implanted upper and lower punches. Using these techniques, we made thin arc-shaped rare-earth bonded magnets (maximum thickness of 0.9 mm) for small magnet motors whose output power was less than 1 W. Both high motor efficiency and high mechanical output power were obtained for magnet made by the powder compacting press, compared with magnet made by the extrusion molding.

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Epoxy resin is generally used as a binder for consolidating Nd-Fe-B melt-spun powder into a specific shape, because the usage of this binder enables us to obtain a density higher than that of other polymers. Reports concerning methods of recycling melt-spun powder included in epoxy resin bonded magnets, however are sparse. We newly therefore developed a technique for recycling Nd-Fe-B melt-spun powder, using liquid-phase pyrolysis of cured epoxy in solvent, and prepared Nd-Fe-B bonded magnets using the recycled powder. This paper reports the new technique for recycling Nd-Fe-B melt-spun powder and evaluates both magnetic properties of the bonded magnets prepared from recycled melt-spun powder and characteristics of a small motor using the recycled magnets.

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Collective magnetic properties were studied for randomly dispersed ferromagnetic fine particles with dipolar interactions. The sample was a frozen iron-nitride magnetic fluid containing uniform single-domain particles. The results show divergences of non-linear susceptibility and of relaxation time. These indicate the existence of a spin glass-like phase transition. At lower temperatures, novel aging phenomena were observed as seen in spin glasses.

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Hall resistance (HR) of a cross-shaped NiFe wire of submicron scale was investigated experimentally and numerically. We found that the HR curve showed various properties depending on the direction of the magnetic field and that the HR had three jumps corresponding to the switching fields in each probe. In order to control the magnetic fields where the HR shows the jumps, the effect of the pad pattern connecting to the wire on the switching field was investigated. The minor loop of the HR was also studied.

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Temperature (T) dependence of the galvanomagnetic effect of very narrow Ni wire was investigated at temperatures below 1 K. A resistance increase proportional to T^-1/2 was observed in the temperature range of 0.1 K < T < 1 K, created through electron-electron interaction. Below 0.1 K, suppression of the resistance rise was observed in the absence of magnetic field.

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Molecular orbital calculations based on Pauli principle and Hund rule reveal spin-polarized electronic states of pyramidal zinc blende nanostructures. Four models of pyramidal clusters, comprising six layers, were constructed with the cluster axes parallel to the crystallographic <111> and <100> axes in the zinc blende. Dangling bonds of the bottom of the cluster are terminated by H atoms. The spin multiplicities of the clusters were estimated for GaN, GaAs, and Si. Highly spin-polarized states were induced by the unpaired electrons on the surfaces of the nanostructures. The clusters present paramagnetic properties. The results were compared with the first-principles calculations for GaN, which indicated feasibility of our phenomenological method. Peculiar size dependent properties of spin polarization of pyramidal nanostructures are suggested for fine magnetic measurement.

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Spin-valve-type tunnel junctions with structure of Ta(5nm)/Ni₇₉Fe₂₁(3 nm)/Cu(20 nm)/Ni₇₉Fe₂₁(3 nm)/Ir₂₂Mn₇₈ (10 nm)/Co₇₅Fe₂₅(4 nm)/Al(0.80 nm)-oxide /Co₇₅Fe₂₅(4 nm)/Ni₇₉Fe₂₁(20 nm)/Ta(5 nm) were fabricated using a microfabrication technique. The optical lithography combined with Ar ion-beam etching and CF₄ active etching was used to pattern the junction area with the size from 100x100 down to 3x3 μm². A thinner barrier layer and a short plasma-oxidation time for Al-oxide layer were used in order to reduce the junction resistance and increase the TMR ratio. High TMR ratio of 69.1% at 4.2 K and 49.7% at room temperature were achieved. A spin-electron polarization tunneling model, based on magnon emission or absorption by the tunneling electrons during the tunnel process, was extended by defining an anisotropic wavelength cutoff energy of spin-wave in this work. Intrinsic magnetoelectric properties, such as the temperature dependence of TMR ratio and resistances from 4.2 to 300 K at 1.0 mV bias can be self-consistently evaluated using this extended model and a unique set of intrinsic parameters.

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Physical properties of SrRu_0.9T_0.1O₃ (T = 3d transition metal) show a clear change between Mn and Fe with increasing atomic number. The magnetic transition temperature is 160 to 180 K from Ti to Mn and less than 150 K from Fe to Zn. The electrical resistivity shows a metallic behavior with a peak at the magnetic transiton temperature in Ti- to Mn -substitution systems and shows a hopping type semiconductive behavior in Fe- to Zn -substitution systems.

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FeWO₄ is an antiferromagnet with T_N= 70 K. A Mössbauer spectroscopy measurement shows that the hyper-fine field is 41.2 kOe at 4.2 K. This small hyper-fine field suggests that a large orbital current which is induced by the spin-orbit interaction, cancels a large part of the magnetic field caused by electron spins. From the fact that most of the hyper-fine fields in Fe²⁺ high-spin compounds have values smaller than those expected from S = 2, we have to consider the effect of orbital magnetic current.

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Perovskite-related Ga oxide, Sr₃(Ga_1-xMn_x)₂O₆ (0≤x≤0.2) was synthesized and characterized in order to design new diluted magnetic perovskites for spin electronics. The crystal structure of Sr₃(Ga_1-xMn_x)₂O₆ (SGMO) was investigated by powder X-ray diffraction and Rietveld analysis. Knowledge of the SGMO was refined using the Rietveld program, RIETAN. Strontium gallate Sr₃Ga₂O₆ (SGO) is a novel cubic structure with GaO₄ tetrahedral unit, space group P3a, and a=b=c=16.095 Å. The crystal structure of SGMO is similar to that of SGO, and Mn-doping does not affect the crystal structure of the mother compound SGO. The electronic nature of Ga and Mn ions in SGMO was investigated by X-ray photoemission spectroscopic measurement, suggesting that the ions of Ga and Mn are +3 and +4 states, respectively. Magnetic properties of SGMO were measured on a SQUID magnetometer. SGMO exhibits non-paramagnetic behavior at 10 K, but it is paramagnetic with θ_P<0 at 300 K.

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Magnetization of Eu_0.58Sr_0.42MnO₃ was measured under hydrostatic pressures up to 0.8 GPa in order to investigate the effect of pressure on the metal-insulator transition, which was investigated at high pressure by resistivity measurements. At ambient pressure, below about 45 K, the magnetization vs temperature curve reveals a spin-glass behavior as reported for a previous experiment. With increasing pressure, the magnetization increases at both 0.005 T and 0.5 T, and a cluster-glass behavior appears at 0.5 T above 0.37 GPa. On the other hand, the magnetization increases with increasing pressure at 1.5 T and 5.0 T. We also found that the high-field susceptibility increases linearly with increasing pressure at a rate of (dχ_hf/dp) = 0.0336(6)μ_BT^-1 GPa^-1.

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Magnetic and magnetotransport properties of polycrystalline La_1-xSr_xMnO₃ (LSMO) thin films annealed at high temperatures were investigated. The reaction of the LSMO thin films with YSZ substrates effectively induces enhancement of low-field MR up to 13.8 % at 78 K for the film annealed at 1350°C. The results are consistently explained by the formation of potential barriers at grain boundaries by the annealing.

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