Amorphous (Sm0.8Zr0.2)1.1(Fe0.9Co0.1)11.3Ti0.7 samples prepared by the rapid-quenching method were annealed under various conditions (8481223 K and 160 min) in a pure Ar atmosphere (PO2 < 1012 Pa). The powders obtained at low annealing temperatures (<1073 K) were predominantly composed of the 1-9 phase (SmFe9), whereas those obtained at high annealing temperatures (>1123 K), were mostly composed of the 1-12 phase (ThMn12). However, the highest coercivity (Hc) of more than 400 kAm11 (5 kOe) was observed for samples containing a mixture of the 1-9 and 1-12 phases, which were obtained by annealing at intermediate temperatures of 11231173 K for 1030 min. Domain structure observations revealed that the sample with the highest Hc (magnetic anisotropy field (Ha) of approximately 6 MAm11) was composed of single-domain particles. Moreover, Hc was decreased to approximately 160 kAm11 (2 kOe) by the formation of a domain structure (approximately 500 nm in width) in samples of the 1-12 mono-phase, despite high Ha of approximately 9 MAm11. A mechanism for these coercivity variations is proposed.
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