Origin of coercivity in an anisotropic Sm(Fe,Ti,V)12-based sintered magnet
Origin of coercivity in an anisotropic Sm(Fe,Ti,V)12-based sintered magnet
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各向异性 Sm(Fe,Ti,V)12 基烧结磁体矫顽力的起源
DOI：
10.1016/j.actamat.2021.117161
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发表时间：
2021
期刊：
影响因子：
9.4
通讯作者：
K. Hono
中科院分区：
文献类型：
--
作者：
J. Zhang;Xin Tang;H. Sepehri;A. Srinithi;T. Ohkubo;K. Hono
采用常规液相烧结工艺，对名义成分为Sm8Fe73.5Ti8V8Ga0.5Al2（at.%）的氮气流磨粉末进行烧结，获得了具有足够大矫顽力μ 0 Hc = 1.0T和剩磁比Mr/Ms = 0.84的各向异性块体SmFe_（12）基烧结磁体。μ 0 Ms = 0.74T的中等饱和磁化强度是由于大量稳定元素Ti、V和Al溶解在1：12相中。主1：12相的各向异性场确定为µ 0 HA =10.2 T。通过扫描电子显微镜（SEM）和扫描透射电子显微镜（STEM）进行的详细多尺度显微结构表征表明，磁体由Sm（Fe，Ti，V，Al）12晶粒组成，具有ThMn 12型晶体结构，尺寸分布为~3 − 15 µm，被~3 nm厚的富Sm非晶间相包裹。第二相包括富金属（Sm，Ga）相、SmOx相和Fe 2（Ti，V）相，与1：12相共存。测得的角度依赖性的磁化强度遵循Kondorsky型磁化反转，这表明磁化强度的出现是由于钉扎的磁畴壁。磁光克尔效应（MOKE）显微镜显示磁化反转开始于晶界和相间界面和薄的非晶间相作为钉扎网站对磁畴壁传播。通过拟合Kronmüllar方程估计的小微磁参数α~0.164表明，减小晶粒尺寸和将晶间相设计为贫铁成分对于将磁化率提高到µ 0 HA/3 = 3.4 T是必要的。这项工作提供了一个最佳的微观结构，以开发具有足够大的矫顽力的各向异性块体SmFe 12基烧结磁体的指导方针。
We have demonstrated an anisotropic bulk SmFe12-based sintered magnet with sufficiently large coercivity ofμ0Hc=1.0 T and a remanence ratio (Mr/Ms) of 0.84 using conventional liquid sintering process of nitrogen jet-milled powders with the nominal composition of Sm8Fe73.5Ti8V8Ga0.5Al2(at.%). The moderate saturation magnetization ofμ0Ms=0.74 T is due to the dissolution of a large amount of stabilizing elements, Ti, V, and Al, in the 1:12 phase. The anisotropy field of the main 1:12 phase was determined to be µ0HA=10.2 T. Detailed multi-scale microstructure characterizations by scanning electron microscope (SEM) and scanning transmission electron microscope (STEM) showed the magnet consists of Sm(Fe,Ti,V,Al)12grains with the ThMn12-type crystal structure with a size distribution of ~3 − 15 µm that are enveloped by ~3 nm thick Sm-rich amorphous intergranular phase. Secondary phases including metallic (Sm,Ga)-rich, SmOx, and Fe2(Ti,V) phases coexist with the 1:12 phase. Measured angular dependence of coercivity follows Kondorsky type magnetization reversal, suggesting the coercivity arises due to the pining of magnetic domain walls. Magneto-optical Kerr effect (MOKE) microscopy revealed magnetization reversal starts at the grain boundaries and interphase interfaces and thin amorphous intergranular phases act as the pinning sites against magnetic domain wall propagation. Small micromagnetic parameterα~0.164 estimated by fitting to the Kronmüllar equation suggest that the reduction of the grain size and engineering of the intergranular phase to an Fe-lean composition are necessary to improve the coercivity toward µ0HA/3 = 3.4 T. This work provides guidelines on an optimum microstructure to develop an anisotropic bulk SmFe12-based sintered magnet with a sufficiently large coercivity.