Fe 基金属－酸化物グラニュラー構造薄膜の巨大磁気抵抗と Hall 効果

抄録

Tunnel-type giant magnetoresistance (GMR) and the Hall effect in Fe-based metal-oxide granular thin films of Fe- Mg-O and Fe-Al-O were investigated. While the magnetoresistance Δρ/ρ₀ (%) of the films at RT was smaller than about 4%, it was remarkably enhanced at lower temperatures, with values of 14% for Fe₂₅Mg₃₂O₄₃ and 25% for Fe₄₄Al₁₇O₃₉ at 4.2 K. These MR values are comparable to or larger than that for Co-Al-O granular thin films at 4.2K (17% at maximum). This result supports the current understanding that the magnitude of tunnel-type GMR is dependent on the spin polarization. The extraordinary Hall coefficients R_s was successfully measured in the metallic conduction region of ρ₀ (μΩcm)<10⁵ for Fe-Mg-O. The R_s vs. resistivity ρ₀. curve can be fitted by R_s ∝ρ₀ ^1.0 for ρ₀<10³, implying skew scattering. However, Rs deviates greatly below the fitting line for 10³<ρ₀< 10⁵ near the tunnel conduction region.