Strain behavior and lattice dynamics in Ni50Mn35In15

TL;DR

This study investigates the lattice dynamics and strain behavior of the Ni50Mn35In15 shape-memory alloy using resonant ultrasound spectroscopy, revealing details about its phase transitions, magnetic states, and lattice stiffening phenomena.

Contribution

It provides new insights into the temperature-dependent lattice and magnetic transitions in Ni50Mn35In15 through RUS measurements, highlighting the magneto-structural coupling and twin wall dynamics.

Findings

Strong lattice stiffening at martensitic transition

Weak magnetoelastic coupling at Curie temperatures

High acoustic damping due to twin wall motion

Abstract

The lattice dynamics in the polycrystalline shape-memory Heusler alloy Ni$_{50}$Mn$_{35}$In$_{15}$ has been studied by means of resonant ultrasound spectroscopy (RUS). RUS spectra were collected in a frequency range $100-1200$ kHz between 10 and 350 K. Ni$_{50}$Mn$_{35}$In$_{15}$ exhibits a ferromagnetic transition at 313 K in the austenite and a martensitic transition at 248 K accompanied by a change of the magnetic state. Furthermore it displays a antiferromagnetic to ferromagnetic transition within the martensitic phase. We determined the temperature dependence of the shear modulus and the acoustic attenuation of Ni$_{50}$Mn$_{35}$In$_{15}$ and compared it with magnetization data. Following the structural softening, which accompanies the martensitic transition as a pretransitional phenomenon, a strong stiffening of the lattice is observed at the martensitic magneto-structural transition. Only a weak magnetoelastic coupling is evidenced at the Curie temperatures both in austenite and martensite phase. The large acoustic damping in the martensitic phase compared with the austenitic phase reflects the motion of the twin walls, which freezes out in the low temperature region.