First-principles study of Ni-Co-Mn-Sn alloys with regular and inverse Heusler structure.

Highlights • Magnetic and structural properties of Ni(Mn) 1.75 Co 0.25 Mn(Ni) 1+x Sn 1-x are studied. • For both alloys, austenite-martensite transition realizes at high Mn (Ni) content. • Ferrimagnetic order is favorable for Mn-Co-Ni-Sn in austenite and martensite. • Magnetization changes greatly at structural transition for Ni-Co-Mn-Sn (x = 0.75). Abstract The influence of partial Mn and Co content on magnetic properties and martensitic transformation in full Heusler compounds Ni-Co-Mn-Sn with the regular and inverse structure is studied theoretically by first-principles calculations within density functional theory. The optimized lattice parameters, magnetic moments and bulk moduli are calculated. It is shown that the substitution of Sn for Mn atom in the regular structure and of Sn for Ni atom in the inverse structure leads to an appearance of stable martensitic phase. For both considered systems with excess Ni and Mn content, the magnetic reference state of austenite and martensite is found to be the ferrimagnetic one except for Ni 1.75 Co 0.25 Mn 1.75 Sn 0.25 . For the latter, martensitic and austenitic phases are ordered ferri- and ferromagnetically that results in a large change in magnetization. [ABSTRACT FROM AUTHOR]