Magnetic Properties of Multifunctional $^7$LiFePO$_4$ under Hydrostatic Pressure

TL;DR

This study uses high-pressure muon spin rotation to explore how hydrostatic pressure influences the magnetic order in LiFePO4, revealing unexpected increases in magnetic transition temperature and magnetic moment.

Contribution

It provides new experimental insights into the pressure dependence of magnetic properties in LiFePO4 using high-pressure $bc^+$SR techniques.

Findings

Magnetic ordering temperature increases under high pressure

Ordered magnetic moment increases with pressure

Contradicts previous theoretical predictions

Abstract

LiFePO$_4$ (LFPO) is an archetypical and well-known cathode material for rechargeable Li-ion batteries. However, its quasi-one-dimensional (Q1D) structure along with the Fe ions, LFPO also displays interesting low-temperature magnetic properties. Our team has previously utilized the muon spin rotation ($\mu^+$SR) technique to investigate both magnetic spin order as well as Li-ion diffusion in LFPO. In this initial study we extend our investigation and make use of high-pressure $\mu^+$SR to investigate effects on the low-$T$ magnetic order. Contrary to theoretical predictions we find that the magnetic ordering temperature as well as the ordered magnetic moment increase at high pressure (compressive strain).