Predictions of magnetism in transition metal aluminides

The Stoner Model has been used to investigate the stability of ferromagnetism in FeAl and the analogous series 3d transition metal aluminide compounds. Stoner factors, N(EF)I, were calculated from augmented plane wave (APW) electronic structure calculations based on local density approximation (LDA), using the Janak formalism. The Stoner criteria [N(EF)I>1] predicts ferromagnetism in FeAl for lattice parameters larger than 5.44 a.u., which is less than the experimental lattice constant of 5.50 a.u., but greater than the APW–LDA minimum energy lattice constant. The Stoner factors for ordered transition metal aluminides in the B2 (CsCl) structure agree reasonably well with those calculated using a rigid band approach, starting from FeAl and shifting EF to simulate the remainder of the series. These Stoner factors predict ferromagnetism for CrAl and MnAl and, assuming the rigid band approximation, for FeAl alloyed with Cr and Mn to the level of Fe0.8Cr0.2Al and Fe0.6Mn0.4Al.