The giant effect of magnetic ordering on a sound velocity in a sigma-Fe55Cr45 alloy

TL;DR

This study reveals that magnetic ordering significantly increases the sound velocity in sigma-FeCr alloys, indicating a magnetically-induced lattice hardening effect.

Contribution

It provides the first detailed atomic dynamics analysis showing the impact of magnetic states on phonon density of states and sound velocity in sigma-FeCr alloys.

Findings

Sound velocity increases by approximately 36% in magnetic phase

Magnetic ordering causes a significant change in phonon density of states

Lattice hardening is induced by magnetic state transition

Abstract

We studied atomic dynamics of sigma-Fe(100-x)Cr(x) (x=45 and 49.5) alloys using nuclear inelastic scattering of synchrotron radiation. For the sigma-Fe55Cr45 alloy, the derived reduced iron-partial density of phonon states reveal a huge difference in the low-energy region between magnetic and paramagnetic states. The latter implies a ca.36% increase of the sound velocity in the magnetic phase, which testifies to a magnetically-induced hardening of the lattice.