Interaction of Phase Transformation and Magnetic Properties of Heusler Alloys: A Density Functional Theory Study

The structural, electronic, and magnetic properties of functional Ni-Mn-Z (Z = Ga, In, Sn, and Sb) Heusler alloys are studied by first-principles and Monte Carlo tools. The ab initio calculations give a basic understanding of the underlying physics that are associated with the complex magnetic behavior arising from the competition of ferromagnetic and antiferromagnetic interactions with increasing chemical disorder in the super cell. This complex magnetic ordering is the driving mechanism of structural transformations. It also essentially determines the multifunctional properties of the Heusler alloys such as magnetic shape-memory and magnetocaloric effects. The thermodynamic properties can be calculated by using the ab initio magnetic exchange parameters in finite-temperature Monte Carlo simulations. The experimental entropy and specific heat changes across the magnetostructural transition are accurately reproduced by the Monte Carlo simulations. The predictive power of the first-principles calculations allows one to optimize the functional features by choosing optimal compositions.