Structure and tunable temperature coefficient of magnetization of Mn_4-xGa_xC alloys prepared by induction melting method

The magnetization of most magnetic materials decreases monotonically with increasing temperature. In this work, we found that the temperature coefficient of magnetization of Mn_4-xGa_xC alloys can be tuned from negative values to positive values by controlling the composition x. The antiperovskite-type Mn_4-xGa_xC (0.05≤x≤0.75) alloys were prepared by using induction melting method, which is more efficient in large-scale production and obtaining full-density alloys in comparison with the traditional solid-state-reaction method. The values of the temperature coefficient of magnetization of Mn_4-xGa_xC change continuously from negative to positive with decreasing x. The Mn_4-xGa_xC alloys with highly thermal-stable magnetization is expected to present in the composition range of 0.15<x<0.25. The saturation magnetization of Mn_4-xGa_xC increases with increasing x, owing to the reduced number of antiferromagnetically coupled Mn atoms at the cubic corner with the face-centered Mn atoms. Most Mn_4-xGa_xC alloys with varying x display near-zero remanent magnetization and coercivity at room temperature. The Currie temperature of Mn_4-xGa_xC decreases with increasing x. The x-ray photoelectron spectra of Mn 2p, Ga 2p, and C 1 s reveal distinct splitting due to the diverse chemical states of these atoms at different lattice positions and/or phases. Our work has developed a class of alloys capable of offering a desired temperature coefficient of magnetization across a broad temperature range, thereby offering a method to manipulate the thermodynamics of magnetization.