Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Microstructure of Materials
Preparation of High-Coercivity Magnetic Powder via Heat Treatment of a Rapidly Quenched Amorphous Starting Compound with a ThMn12 Structure
Tomoko KunoTakahide YamamotoKimiko UrushibataKurima KobayashiSatoshi Sugimoto
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2020 Volume 61 Issue 4 Pages 657-662


Amorphous (Sm0.8Zr0.2)1.1(Fe0.9Co0.1)11.3Ti0.7 samples prepared by the rapid-quenching method were annealed under various conditions (848–1223 K and 1–60 min) in a pure Ar atmosphere (PO2 < 10−2 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 kAm−1 (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 1123–1173 K for 10–30 min. Domain structure observations revealed that the sample with the highest Hc (magnetic anisotropy field (Ha) of approximately 6 MAm−1) was composed of single-domain particles. Moreover, Hc was decreased to approximately 160 kAm−1 (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 MAm−1. A mechanism for these coercivity variations is proposed.

Fig. 5 Variation of Hc for the samples subjected to heat treatment under various conditions. Fullsize Image
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© 2020 The Japan Institute of Metals and Materials
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