Effect of external pressure on the magnetic properties of LnFeAsO (Ln = La, Ce, Pr, Sm)

TL;DR

This study examines how external pressure influences magnetic order in LnFeAsO compounds, revealing lanthanide-dependent effects on magnetic transition temperatures and Fe magnetic moments through experimental and computational methods.

Contribution

It provides new insights into the pressure dependence of magnetic properties in LnFeAsO and assigns a precise value to the Fe magnetic moment using combined experimental and ab-initio approaches.

Findings

Magnetic transition temperature decreases with pressure

Fe magnetic moment reduces under external pressure

Lanthanide dependence observed in magnetic response

Abstract

We investigate the effect of external pressure on magnetic order in undoped LnFeAsO (Ln = La, Ce, Pr, La) by using muon-spin relaxation measurements and ab-initio calculations. Both magnetic transition temperature $T_m$ and Fe magnetic moment decrease with external pressure. The effect is observed to be lanthanide dependent with the strongest response for Ln = La and the weakest for Ln = Sm. The trend is qualitatively in agreement with our DFT calculations. The same calculations allow us to assign a value of 0.68(2) $\mu_B$ to the Fe moment, obtained from an accurate determination of the muon sites. Our data further show that the magnetic lanthanide order transitions do not follow the simple trend of Fe, possibly as a consequence of the different $f$-electron overlap.