2相ナノ結晶材料の粒間磁気結合と保磁力

概要

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Bcc/amorphous two-phase nanocrystalline samples with various volume fractions of the amorphous phase were prepared from a melt-spun precursor amorphous Fe_<91>Zr_7B_2 alloy. The coercivity of the sample at 77 K, well below the Curie temperature of the intergranular amorphous phase (T_c^<am> ≈ 370 K), shows a tendency to decrease with increasing the volume fraction of the amorphous phase (V_<am>). This suggests that the magnetocrystalline anisotropy energy of the sample is diluted by the volume of the residual amorphous phase when the intergranular coupling is stiff. On the other hand, the coercivity at 450 K, well above Tc^<am>, increases dramatically with increasing V_<am>. This indicates that the intergranular magnetic coupling above T_c^<am> depends on the intergranular distance. The stiffness of ferromagnetic coupling in the intergranular region above T_c^<am> was estimated to be 〜10^<-14> to 10^<-13> J/m^2. The coercivity at T 〜 T_c^<am> appears to vary as the -6^<th> power of the spontaneous magnetization of the intergranular amorphous phase when V_<am> is relatively large.
2000-04-15