An alternative approach to the measurement of anisotropy field – Single grain extraction

A fast and cost effective way to determine the anisotropy field (µ₀H_a) and the saturation magnetization (µ₀M_s) of a hard magnetic compound is crucial to search for new permanent magnet materials. A single crystal in a defined shape is the conventional way to determine µ₀H_a. However, the growth of phase-pure single crystalline sample is not always possible for some hard magnetic compounds with poor phase stability. In this study, we propose and demonstrate a fast and cost-effective method for determining µ₀H_a and µ₀M_s of a main phase in complex alloys. For this purpose, a single grain in trapezoidal prism shape was micro-sampled from bulk heterogeneous (Sm_0.8Zr_0.2)(Fe_0.8Co_0.2)_11.5Ti_0.5 ingot using focused ion beam, from which the magnetization and the anisotropy filed of the ThMn₁₂-type phase in the alloy was determined to be μ₀M_s = 1.53 T and µ₀H_a = 8.2 T. Electron backscattered diffraction (EBSD) was carried out prior to the lift-out process to select desired region with a known c-axis direction, parallel to the lift out direction in this work. The reliability of this technique was tested by comparing the result with that for the (Nd_0.9Dy_0.1)₂Fe₁₄B single crystal.