Soft X-ray absorption spectroscopy and magnetic circular dichroism under pulsed high magnetic field of Ni-Co-Mn-In metamagnetic shape memory alloy

TL;DR

This study uses pulsed high magnetic fields to perform X-ray absorption spectroscopy and magnetic circular dichroism on Ni-Co-Mn-In alloy, revealing element-specific magnetic moments and phase transformations related to metamagnetic behavior.

Contribution

It provides detailed element-specific magnetic moments and insights into phase transformations under high magnetic fields in Ni-Co-Mn-In alloy, a novel application of pulsed-field XAS and MCD techniques.

Findings

Magnetic moments of Mn in austenite phase quantified

Field-induced reverse transformation observed via MCD signals

Ni 3d-electrons mainly drive martensitic transformation

Abstract

In this study, X-ray absorption spectroscopy (XAS) experiments for Ni45Co5Mn36.7In13.3 metamagnetic shape memory alloy were performed under high magnetic fields up to 12 T using a pulsed magnet. Field-induced reverse transformation to austenite phase caused considerable changes in the magnetic circular dichroism (MCD) signals and the magnetic moments of the ferromagnetic coupling between Mn, Ni, and Co were determined. The spin magnetic moment, Mspin, and orbital magnetic moment, Morb, of Mn atom in the induced austenite ferromagnetic phase, estimated based on the magneto-optical sum rule, were 3.2 and 0.13 {\mu}B, respectively, resulting in an Morb / Mspin ratio of 0.04. In the element-specific magnetization curves recorded at 150 K, metamagnetic behavior associated with the field-induced reverse transformation is clearly observed and reverse transformation finishing magnetic field and martensitic transformation starting magnetic field are detected. There was almost no difference in the magnetically averaged XAS spectrum for Mn-L2,3 edges between in the martensite and in the magnetic field-induced austenite phases, however, it was visible for Ni, indicating that Ni 3d-electrons mainly contribute to martensitic transformation.