Evolution of phase structure and magnetic property with Mn content and heat treatment in Fe3-Mn Ga alloy

The evolution of structure and magnetic property with Mn content and different heat- treatment in Fe3-xMnxGa alloy has been investigated in this study. First-principles calculations suggest that the small energy difference between the different structures of Fe3Ga and Fe2MnGa alloys leads to the instability of them. The phase transformation for samples being quenched from 623 K, 883 K, 1073 K and the ribbons are studied with X-ray diffraction. Body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal structures are observed and the schematic phase diagram is given in this paper. Together with the theoretical calculation moments for Fe3Ga and Fe2MnGa with different crystal structures and magnetic configurations, the magnetic properties are discussed. The saturation magnetization MS of bcc and hexagonal Fe3-xMnxGa samples at 5 K gradually decreases with increasing Mn content, which can be attributed to the increase of the fraction of Fe-Mn antiferromagnetic (AFM) coupling. In fcc Fe2MnGa, with the increase of quenching temperature from 623 K to 1073 K, more ferrimagnetic (FIM) coupling phase with higher energy is formed, showing a decrease of MS and unsaturation of magnetization under the test magnetic field in MH curve. A magnetic field induced AFM to FIM state transition is found in Fe2MnGa alloy with L12 type of atomic disorder when quenched from 1073 K. The tunable structure and magnetic properties make it has the potential applications in versatile material field.