Local Atomic Structure of Martensitic Ni$_{2+x}$Mn$_{1-x}$Ga: An EXAFS Study

TL;DR

This study uses EXAFS measurements to analyze the local atomic structure and atomic rearrangements in Ni$_{2+x}$Mn$_{1-x}$Ga alloys during martensitic transformation, revealing atomic shuffling and orbital hybridization changes.

Contribution

It provides new insights into the atomic-level structural changes and orbital hybridization associated with martensitic transformation in Ni-Mn-Ga alloys.

Findings

Identification of atomic shuffling amplitudes.

Observation of hybridization changes in Ga-p and Ni-d orbitals.

Detection of local symmetry breaking during transition.

Abstract

The local atomic structure of Ni$_{2+x}$Mn$_{1-x}$Ga with 0 $\le$ $x$ $\le$ 0.16 alloys was explored using Mn and Ga K-edge Extended X-ray Absorption Fine Structure (EXAFS) measurement. Inorder to study the atomic re-arrangements that occur upon martensitic transformation, room temperature and low temperature EXAFS were recorded. The changes occurring in the L2$_1$ unit cell and the bond lengths obtained from the analysis enables us to determine the modulation amplitudes over which the constituent atoms move giving rise to shuffling of the atomic planes in the modulated structure. The EXAFS analysis also suggests the changes in hybridization of Ga-$p$ and Ni-$d$ orbitals associated with the local symmetry breaking upon undergoing martensitic transition.