The Effect of Mn/Al Substitution on the Structural Stability and Magnetic Properties of Mn3AlC

The structural stability and magnetic properties of Mn3+xAl1-xC antiperovskite with varied Mn/Al substitution were studied systematically. Single phase Mn3+xAl1-xC alloys with antiperovskite structure were obtained in samples with x = -1/4, 0, 1/4, 1/2. An additional Mn23C6 phase was precipitated from Mn3+xAl1-xC antiperovskite for x = 3/4 while Mn23C6 phase was formed as major phase for x = 1. The mutual substitution of Mn and Al atoms has substantial effect on the Curie temperature and the saturation magnetization of the Mn3+xAl1-xC alloys. In comparison with the as-cast alloys, the as-annealed Mn3+xAl1-xC alloys exhibit reduced Mn/Al substitutions after high temperature homogenization, which enhances the ordering of Mn and Al atoms in the lattices. The Curie temperature of the homogenized Mn3+xAl1-xC increases with increasing Mn substitution to Al. The Mn3AlC alloy shows the highest saturation magnetization among all samples with varied Mn/Al ratios. Most samples show zero coercivity and zero remanent magnetization. The maximum value of the magnetic entropy changes of Mn2.75Al1.25C at 285 K is 2.26 J/kg K in fields up to 3 T.