Effect of external pressure on the magnetic properties of $R$CoAsO ($R$ = La, Pr, Sm): a $\mu$SR study

TL;DR

This study investigates how external hydrostatic pressure affects the magnetic properties of RCoAsO compounds using muon spin spectroscopy, revealing weak pressure dependence in La and Sm variants and complex behavior in Pr variant.

Contribution

It provides new insights into the pressure effects on magnetic properties of RCoAsO compounds, highlighting differences among La, Pr, and Sm variants and contrasting with related compounds RCoPO.

Findings

Magnetic properties of LaCoAsO and SmCoAsO are largely unaffected up to 2.4 GPa.

PrCoAsO shows a complex pressure-dependent behavior, possibly due to muon site population changes.

Chemical pressure from As/P substitution in RCoPO differs from external pressure effects.

Abstract

We report on a detailed investigation of the itinerant ferromagnets LaCoAsO, PrCoAsO and SmCoAsO performed by means of muon spin spectroscopy upon the application of external hydrostatic pressures $p$ up to $2.4$ GPa. These materials are shown to be magnetically hard in view of the weak dependence of both critical temperatures $T_{C}$ and internal fields at the muon site on $p$. In the cases $R$ = La and Sm, the behaviour of the internal field is substantially unaltered up to $p = 2.4$ GPa. A much richer phenomenology is detected in PrCoAsO instead, possibly associated with a strong $p$ dependence of the statistical population of the two different crystallographic sites for the muon. Surprisingly, results are notably different from what is observed in the case of the isostructural compounds $R$CoPO, where the full As/P substitution is already inducing a strong chemical pressure within the lattice but $p$ is still very effective in further affecting the magnetic properties.