High-temperature properties and enhanced magnetic properties by magnetic field heat treatment of D022 Mn3−xGa (x = 0, 0.2, and 0.4) alloys

In situ high-temperature XRD and magnetic field heat treatment (MFHT) under a magnetic field of 50 kOe have been used to investigate the structural and magnetic properties of the D022 Mn3−xGa (x = 0, 0.2, and 0.4). It was found that Mn3−xGa compounds maintain ferrimagnetic D022 phase in the temperature range of 300–700 K, and their magnetic properties were remarkably improved through MFHT. The saturation magnetization (Ms) of Mn3.0Ga at 300 K increased by 37% from 18.3 to 25.0 emu/g after MFHT. All Mn3-xGa samples showed superior thermal stability in magnetization from 300 to 500 K, and they still retained excellent magnetic properties at a temperature of up to 700 K. The magnetization of Mn3.0Ga and Mn2.8Ga showed a positive temperature coefficient from 300 to 400 K. Even at 700 K, Ms and Hc of 24.3 emu/g and 4.5 kOe were retained in Mn2.8Ga, which is excellent for high-temperature applications. In addition, the coercivity mechanism of Mn3−xGa at 700 K was illustrated by minor hysteresis loops measurement, and it was found that the coercivity mechanism of Mn3−xGa at 700 K was dominated by the pinning mechanism.