Effect of Changing Stoichiometry on the Magnetic properties of NiFe­­MnAl

In recent years, there has been significant research, both experimental and theoretical, focused on exploring the potential of half-metallic Heusler alloys for spin-transport based applications. NiFeMnAl has been predicted to exhibit half-metallic properties with Curie temperature of about 470 K. We have investigated how the structural and magnetic properties of this alloy change when its stoichiometry is modified by changing the concentrations of Fe and Mn, and also by doping the Mn site with Co. We studied the structural and magnetic properties of NiFe_1.75Mn_0.25Al, NiFe_1.5Mn_0.5Al, NiFe_1.25Mn_0.75Al, NiFeCo_0.25Mn_0.75Al, and NiFeCo_0.5Mn_0.5Al prepared by arc melting and annealing. All five of the as-prepared alloys exhibit single phase cubic crystal structures with A2-type disorder. The as-prepared alloys showed saturation magnetization between 75 and 125 emu/g with NiFeCo_0.5Mn_0.5Al showing the highest value when measured at 100 ^oC. There is no change in the crystal structure and a small change in the magnetic properties due to annealing at 500 ⁰C for 6 days.