(Co, Fe)-M-O (M = Ti, Nd, Al, Si) グラニュラートンネル型巨大磁気抵抗効果薄膜における酸化物の比誘電率と強磁性微粒子の粒径の影響(磁性体物理)

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Granular (Co, Fe)-M-O (M = Ti, Nd, Al, and Si) thin films showing giant magnetoresistance (GMR) of 4%-10% at room temperature were successfully prepared by the reactive deposition method using an O_2 beam. The magnetoresistance (MR) ratios at 19 kOe (MR_r(19 kOe)) were found to have roughly a tendency of MR_r(M=Si)<MR_r(Al)<MR_r(Nd)<MR_r(Ti), which corresponds to the order of the estimated relative dielectric constants (ε_r) of amorphous SiO_2, Al_2O_3, Nd_2O_3, and TiO_2. In particular, MR_r (M = Ti, 19 kOe) was found to reach a large value of 9.8 (%). Furthermore, MR_r (H = ∞) value of these films was found to increase abruptly with the decrease in the average diameter of ferromagnetic particles, and is estimated to reach about 15% at room temperature. The phenomenon can be explained by considering that, as the average diameters of ferromagnetic particles decrease, spin-flips of tunnel electrons are suppressed because the energy for inelastic scattering generated at the time of tunneling between particles with different diameters becomes smaller than the minimum magnon energy.
社団法人日本磁気学会の論文
2003-04-01