Modelling of chemical and magnetic order in Ni-Mn-Al shape memory alloys using Monte Carlo simulations

ALÉS, ALEJANDRO; LANZINI, FERNANDO

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

ELSEVIER SCIENCE BV

Año: 2023 vol. 585 p. 171110 - 171110

0304-8853

A model for the description of atomic and magnetic ordering in Ni-Mn-Al shape memory alloys is presented. The parameters characterising the energies of the chemical and magnetic interactions were obtained from fitting to experimental data. Monte Carlo simulations based on this model correctly reproduces the critical B2 L21 ordering temperatures as a function of composition for three pseudobinary composition lines, as well as the nature of the low temperature magnetic transition. A ferromagnetic configuration is predicted for alloys in the stable L21 structure, whereas an antiferromagnetic state is obtained for metastably retained B2 order; this is in agreement with experimental observations. It is verified that atomic ordering is strongly dominated by the interactions between Ni and Al atoms in nearest neighbours. As a consequence, the formation of B2 order can delay the stabilization of the L21 configuration at low temperatures. Since the magnetic interactions change sign with the Mn-Mn distance, the type of stable magnetic configuration depends on atomic ordering.