The structure, intrinsic magnetic properties, and magnetic hardening of L10-Mn1.15Ga alloy

Recently, we successfully prepared L10-ordered Mn1.15Ga alloy with space group P4/mmm by induction melting high purity Mn and Ga followed by annealing the as-melt ingot at 465 °C for 2 days. The highest experimental room-temperature saturation magnetization, Ms, of 92 emu/g, is reported, and the Curie temperature and anisotropy field are estimated to be 595 K and 6.3 T, respectively. Based on the compound, low-energy ball milling technique, along with size-selection and annealing treatment are utilized to study the magnetic hardening and magnetic anisotropy inducement. It was found that milling can effectively improve the coercivity. With increasing the milling time to 210 min, the coercivity gradually increases from 0.8 kOe to a maximum value of 4.71 kOe for powders milled for 120 min, and then decreases. After classifying the powders milled for 120 min into different sizes, the coercivity is caused varying degrees of improvement and up to 5.03 kOe for the particles less than 10 μm. However, the remanence and magnetization are getting worse with long ball-milling time. After annealing at 465 °C for 1 min, remanence and magnetization are recovered without losing too much coercivity, leading to a great promotion of energy product, and the (BH)max of 2.96 MGOe is achieved for the L10-Mn1.15Ga powders with particle size in the range of 20-37 μm. In addition, the annealed powder shows possible magnetic anisotropy. The degree of alignment reaches 0.47 for the L10-Mn1.15Ga powder, which is 18% higher than the as-milled powders with same size distribution.