The effect of chemical disorder on magnetic properties of FeNi and Fe2Ni2N alloys

The dependency of magnetic anisotropy constant Ku on the degree of order for L10-ordered FeNi alloys and tetragonally ordered Fe2Ni2N alloys has been investigated using first-principles calculations with special quasi-random structure. The Ku increases with increasing ordering parameter S for both alloys and the Ku of Fe2Ni2N exceeds that of FeNi in the region above S = 0.5, and more than 1 MJ/m3 of Ku can be expected when the S is 0.67 or higher, reaching more than 2 MJ/m3 for fully ordered Fe2Ni2N. We also investigated the Ku of tetragonally ordered Fe2Ni2N for the tetragonal distortion, and found that the Ku is increased with in-plane compressive stain and reaches 2.2 MJ/m3 with a 1 % compression of in-plane lattice parameter.