First-principles calculation of the instability leading to giant inverse magnetocaloric effects

Abstract

The structural and magnetic properties of functional Ni-Mn-Z (Z = Ga, In, Sn)\nHeusler alloys are studied by first-principles and Monte Carlo methods. The\n\\textit{ab initio} calculations give a basic understanding of the underlying\nphysics which is associated with the strong competition of ferro- and\nantiferromagnetic interactions with increasing chemical disorder. The resulting\n$d$-electron orbital dependent magnetic ordering is the driving mechanism of\nmagnetostructural instability which is accompanied by a drop of magnetization\ngoverning the size of the magnetocaloric effect. The thermodynamic properties\nare calculated by using the \\textit{ab initio} magnetic exchange coupling\nconstants in finite-temperature Monte Carlo simulations, which are used to\naccurately reproduce the experimental entropy and adiabatic temperature changes\nacross the magnetostructural transition.\n