The induced magneto-elastic energy in a thin magnetic film may result from residual stress combined with magnetostriction, which is sensitive to the crystal structure. Thus, it is important to optimize the magnetostriction in giant magnetoresistive sensor stacks that consist of Co, Cu, and NiFe layers. Analysis of the structure, however, is difficult because the lattice constants of the stacks are similar in each layer. Therefore, a peak separation method for x-ray diffraction (XRD) pattern was examined, using the anomalous dispersion effect. The XRD with the scattering vector in the film plane of a Cu/NiFe multilayer was measured at four x-ray wavelengths: the near Cu-K edge, post Cu-K edge, near Ni-K edge, and post Ni-K edge ones. The in-plane XRD profiles of the sample were slightly different from each other. The differential Cu profile was calculated by simple subtraction of the near Cu-K edge profile from the post Cu-K edge one. The differential NiFe profile was calculated by simple subtraction of the near Ni-K edge profile from the post Ni-K edge one. The Cu and NiFe differential peaks were clearly related to each other. This result suggested that it is possible to analyze the crystal structure in each layer of a Co, Cu, and NiFe multilayer stack by using the anomalous dispersion effect.

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Partially ordered L1₀-FePt nanoparticles synthesized in tetraethylene glycol by using polyol process is mostly polycrystalline in nature. In this paper, we attempted the preparation of single crystal L1₀-FePt nanoparticles by introducing nucleating and complexing agents during the synthesis. Though the synthesis of L1₀-FePt particles with constant physical properties was possible by using hexachloroplatinate (H₂PtCl₆) as the nucleating agent, particles remained polycrystalline in nature. However, when carboxylic acid was used along with H₂PtCl₆ FePt nanoparticles with more than 50 % ordering was realized under the optimum experimental conditions of Fe:Pt initial mole ratio of 52.5:47.5, 1 at% H₂PtCl₆ and five equivalent weight of Fe of carboxylic acid. The superlattice reflection lines of (001) and (110) in XRD pattern and the sextets from the Mossbauer spectroscopy at room temperature confirmed the presence of L1₀ phase. The coercivity and anisotropy field of these particles were 5. 6 kOe and more than 40 kOe, respectively.

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The ozone oxidization process of metal Al film for the formation of barriers in magnetic tunnel junctions (MTJs) is investigated. The ozone exposure method, in which atomic oxygen in the ground state is an oxidizing species, is expected to oxidize ultra-thin Al films more mildly than the plasma oxidization method, since the energy level of atomic oxygen is ∼2 eV lower in the ozone method than in the plasma method. The main results were as follows: (1) In the case of ozone oxidation, the diffusion coefficient of oxygen in Al-O is much smaller than in the plasma oxidation case. (2) Ozone oxidation of Al films is spontaneously stopped at the interface to the bottom Co-Fe, regardless of the exposure amount. (3) In the case of plasma oxidation, the exposure condition in which the TMR ratio reaches its maximum shifts with increasing Al layer thickness. However, in the case of ozone oxidation, that exposure condition does not shift, regardless of the Al layer thickness. (4) In MTJs fabricated by ozone oxidation, a high TMR ratio is obtained without annealing. We conclude from all these findings that ozone oxidation of metal Al layers is a promising barrier formation process for realizing high-quality and very thin insulating layers.

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The Fe-Si magnetic film with an Ru underlayer was fabricated and characterized. In the film, the Fe-Si grain became small when using a very thin Ru underlayer. In addition, the surface roughness of Fe-Si film with a thin Ru underlayer became smaller than that without an Ru underlayer. Consequently, the hard axis coercivity of the Fe-Si film with a 1 nm Ru underlayer was about 1.1 Oe, which was much lower than that of the same film without an Ru underlayer. The Fe-Si film with a 1 nm Ru underlayer had a clear uniaxial magnetic anisotropy (anisotropy field H_k: 18 Oe), a hard axis relative permeability of 900, and a ferromagnetic resonance (FMR) at around 1.6 GHz. A very sharp peak of the imaginary part of permeability μ_h" was observed at the FMR frequency. This was due to the clear uniaxial magnetic anisotropy and small anisotropy dispersion.

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The impedance and phase characteristic of a magnetic thin film changes when a magnetic field is applied. The high-frequency-carrier magnetic field sensor, also called a GMI sensor, employs this phenomenon as its principle. We directed our attention to the change in the phase characteristic, and measured the dc magnetic field by measuring the phase as a phase difference, using the dual-mixer time-difference method. We optimized the method and the continuous sampling condition to measure the phase difference, and developed an efficient system for measuring the continuous sampling phase difference with low noise. The system was successfully used to measure the ac magnetic field by continuous sampling of the phase difference of a high-frequency-carrier magnetic field sensor.

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