Electronic Instabilities in Shape-Memory Alloys

TL;DR

This study reveals that electronic structure changes significantly influence the diffusionless transition in shape-memory alloys, with magnetic fields altering transition temperatures and revealing quantum oscillations related to Fermi surface properties.

Contribution

It demonstrates the impact of magnetic fields on the diffusionless transition and uncovers electronic structure effects in shape-memory alloys through thermodynamic and ultrasonic measurements.

Findings

Magnetic fields lower the transition temperature in In-24 at.% Tl.

Quantum oscillations indicate a strong Fermi surface effect in AuZn.

Electronic structure changes are linked to the shape-memory transition.

Abstract

Using a variety of thermodynamic measurements made in magnetic fields, we show evidence that the diffusionless transition (DT) in many shape-memory alloys is related to significant changes in the electronic structure. We investigate three alloys that show the shape-memory effect (In-24 at.% Tl, AuZn, and U-26 at.% Nb). We observe that the DT is significantly altered in these alloys by the application of a magnetic field. Specifically, the DT in InTl-24 at.% shows a decrease in the DT temperature with increasing magnetic field. Further investigations of AuZn were performed using an ultrasonic pulse-echo technique in magnetic fields up to 45 T. Quantum oscillations in the speed of the longitudinal sound waves propagating in the [110] direction indicated a strong acoustic de Haas-van Alphen-type effect and give information about part of the Fermi surface.