Magnetovolume instabilities in the pressure dependence of the K-edge circular dichroism of Fe3C Invar particles

TL;DR

This study investigates how pressure influences the magnetic properties of Fe3C particles, revealing a transition from high to low magnetic moment around 10 GPa through K-edge circular dichroism measurements.

Contribution

It provides the first experimental evidence of pressure-induced magnetovolume instability in Fe3C using K-edge x-ray magnetic circular dichroism.

Findings

Identified a high-moment to low-moment transition at ~10 GPa.

Demonstrated pressure dependence of magnetic circular dichroism in Fe3C.

Confirmed magnetovolume instability in Fe3C under pressure.

Abstract

The p-electrons of carbon in the interstitial compound Fe3C hybridize with the Fe d-band and enhance the valence electron concentration of Fe from 8 to 8.67. At this concentration, substitutional 3d transition metals and alloys exhibit strong moment-volume coupling phenomena and associated magnetovolume instabilities, otherwise known as the Invar effect. For this reason, Fe3C is also expected to incorporate a strong magnetovolume instability, and therefore, we examine the pressure dependence of the of the K edge x-ray magnetic circular dichroism in Fe3C at ambient temperature and pressures up to 20 GPa. We and clear evidence for a high-moment to low-moment transition at about 10 GPa.