Investigation of structural and magnetic properties of Al and Cu doped MnBi alloy

Abstract Alloys of Mn-Bi, MnBi-Al and MnBi-Cu were prepared by arc-melting followed by homogenization treatment. All the alloys exhibited hexagonal NiAs crystal structure. Weight fraction of the Low Temperature Phase (LTP) MnBi phase in the Mn-Bi alloy was found to be 88% with a magnetization of 51 emu/gm at 20 kOe, whereas Al and Cu doping resulted in the decrease of the weight fraction of the LTP MnBi phase as well as saturation magnetization. The coercivity is found to increase with the increase in the doping concentration. Upon ball milling the alloys, phase decomposition and a decrease in the magnetization were observed in undoped Mn-Bi alloy. On the other hand, there was no significant phase decomposition and change in the magnetization in doped MnBi alloys due to ball milling. A change in the magneto structural phase transition temperature of MnBi was observed with doping, which is attributed to the lattice modifications occurring in the MnBi system. Doped and undoped Mn-Bi alloys shows increase in coercivity with temperature. Details of investigation are presented in this paper.