We describe the dynamics of a compensated antiferromagnet (AFM) in the presence of spin-polarized current. The developed phenomenological model is based on the assumption that macrospins corresponding to different sublattices of AFM interact with the spin-polarized current independently. It is shown that spin-polarized current can i) be a source of the "negative friction"; ii) modify spin-wave spectra; and iii) switch the steady state of AFM. The value of the threshold current at which the switching between different steady states of AFM takes place depends upon the anisotropy of magnetic interactions.

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Spin polarization of Cu embedded in Fe₇₀Co₃₀ films has been investigated by means of transmission x-ray magnetic circular dichroism (XMCD). [Fe₇₀Co₃₀(d_FeCo) / Cu(d_Cu)]_n multilayered films were fabricated on Si-N membrane substrate, fixing total thickness of Fe-Co and Cu layers. Magneto-optical sum-rules were applied to the measured absorption and XMCD spectra to determine quantitatively the spin and orbital moments of Cu. With decreasing the Cu layer thickness, the spin moment of Cu increases but exhibits to be saturated about 0.1 μ_B / atom. The small value of spin moment (0.1 μ_B), comparing to that of the 3d transition metals such as Fe and Co, implies that only the top part of 3d down-spin band of Cu is unoccupied in these specimens.

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An Fe-Co-Mn alloy was made by the mechanical alloying method. In order to increase the saturation magnetization, as well as to decrease coercivity, Mn was added to an Fe-Co alloy. An Fe-Co-Mn alloy was made by mechanical alloying, using the Fe-Co alloy and Mn. The coercivity and grain size of the alloy decreased, but the saturation magnetization also decreased. Next, an Fe-Co-Mn alloy was made by mechanical alloying, using Fe, Co, and an Fe-Mn alloy. The coercivity of the alloy increased and the minute effect on the grain size due to Mn addition disappeared, but the reduction ratio of the saturation magnetization also decreased.

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Nd₂Fe₁₄B thin films were fabricated with a DC magnetron sputtering system. X-ray diffraction experiments and the Rietveld analysis showd that the crystallites of the Nd₂Fe₁₄B phase were highly oriented perpendicular to the film plane. In addition to the diffraction peaks originated from the Nd₂Fe₁₄B phase, we observed extra reflections that can be assigned as a NdO phase. The relative intensity, hence the volume fraction of the NdO phase varied depending on the sputtering conditions such as the substrate temperature, Ar gas pressure, and Ta buffer layer thickness. It was found that the magnetization value depends strongly on the Ar gas pressure and reaches a maximum at 0.7 Pa of Ar gas pressure. The maximum magnetization value is 15 kG, which is comparable with the bulk value. The optimized values of the maximum energy product, saturation magnetization, and coercivity are (BH)_max = 36 MGOe, 4πM_s = 14.7 kG, and H_c = 6.7 kOe, respectively.

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A Co/Pt patterned medium was fabricated by an Ar ion etching process through a self-assembled polymer mask with a diameter of 40 nm, and its etching damage was investigated by using the grazing incidence x-ray reflectivity (GIXR) technique. This method is effective for investigating the changes in the morphology of surface and interface. It was found that the surface roughness was increased from 0.5 nm to 3.8 nm by the etching process, while the roughness of the multilayer structure was not changed. Large roughness at the surface is due to the lack of a dot structure as a result of the over-etching condition. The lack of significant damage to the internal multilayer structure is consistent with the lack of significant degradation in the magnetic characteristics. Ar ion etching is found to be robust for fabricating patterned medium with little damage even in the over-etching condition.

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In a previous study, a thick-film Mn-Zn ferrite particle/polyimide composite material for power inductors was developed using screen printing technique. This composite film enabled us to obtain a thin planar power inductor. However, downsizing of the planar inductor required that Mn-Zn ferrite particles be replaced by other magnetic particles with the higher permeability. In this study, we used two powdery magnetic metals to create a thick-film composite material, and fabricated downsized planar inductors using such composites. When used in a step-down chopper dc-dc converter, the fabricated inductors exhibited electric properties equal to those of competitive ready-made inductors, which are thicker than our planar inductor.

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