The nature of the metamagnetic transition in Heusler alloy Ni44.9Mn43In12.1 studied for magnetic refrigeration application

Abstract

The nature of the phases, phase transitions, and their magnetic characteristics all play an essential role in the performance of Ni-Mn-In Heusler alloys, both as magnetic shape memory and giant magnetocaloric effect (MCE) materials. The details of the structural and magnetic transformations in Ni 44.9 Mn 43 In 12.1 Heusler alloy are reported in this work, using synchrotron and neutron diffraction and AC-SQUID susceptibility results. Of special interest is the affirmation of an antiferromagnetic (AFM) phase and the exclusion of a spin-glass state as the cause of the observed drop in magnetization upon cooling. This is of critical importance for magnetocaloric applications because of the dominant contribution to MCE of the magnetic entropy change upon phase transformation. • The magnetic and crystallographic nature of Ni 44.9 Mn 43 In 12.1 , were studied using synchrotron and neutron diffraction and AC-SQUID. • Cooling below 304 K results in ferromagnetic to antiferromagnetic transition; critically important for the magnetocaloric effect. • The crystallographic and magnetic transformations from austenite to martensite and from ferromagnetic to antiferromagnetic, coincide. • The hysteresis of the crystallographic transition is narrow, an advantage for MCE and other applications.