Structural-induced antiferromagnetism in Mn-based full Heusler alloys: The case of Ni2MnAl

We employ ab initio electronic structure calculations and a model Heisenberg Hamiltonian, and show that the Heusler alloy Ni2MnAl exhibits a ferrromagnetic-antiferromagnetic phase transition upon Mn-Al disorder. The transition is triggered by the smaller Mn-Mn nearest-neighbors distance in accordance to the Bethe-Slater curve. Our results explain available experimental data and show that the prevention of disorder is essential to achieve maximum performance in Heusler-based devices. (C) 2011 American Institute of Physics. [doi:10.1063/1.3565246]