Common effect of chemical and external pressures on the magnetic properties of RECoPO (RE = La, Pr)

TL;DR

This study investigates how chemical and external pressures influence the magnetic properties of RECoPO compounds, revealing that local magnetism is dominated by Co sublattice and that pressure enhances magnetic transition temperatures, supported by experimental and theoretical analysis.

Contribution

It demonstrates that chemical pressure from rare-earth substitution and external hydrostatic pressure similarly affect magnetic properties, with insights supported by muon spin spectroscopy and density-functional theory.

Findings

Magnetism is dominated by Co sublattice, not Pr$^{3+}$ ions.

External pressure up to 24 kbar enhances magnetic transition temperature.

Pressure induces a significant change in the band structure of LaCoPO.

Abstract

We report a detailed investigation of RECoPO (RE = La, Pr) and LaCoAsO materials performed by means of muon spin spectroscopy. Zero-field measurements show that the electrons localized on the Pr$^{3+}$ ions do not play any role in the static magnetic properties of the compounds. Magnetism at the local level is indeed fully dominated by the weakly-itinerant ferromagnetism from the Co sublattice only. The increase of the chemical pressure triggered by the different ionic radii of La$^{3+}$ and Pr$^{3+}$, on the other hand, plays a crucial role in enhancing the value of the magnetic critical temperature and can be mimicked by the application of external hydrostatic pressure up to 24 kbar. A sharp discontinuity in the local magnetic field at the muon site in LaCoPO at around 5 kbar suggests a sizeable modification in the band structure of the material upon increasing pressure. This scenario is qualitatively supported by \emph{ab-initio} density-functional theory calculations.