Large Magnetoresistance Effects in $Ln$CoAsO with a Ferromagnetic-Antiferromagnetic Transition

TL;DR

This study reports significant magnetoresistance effects in layered LnCoAsO compounds, linked to ferromagnetic-antiferromagnetic transitions and multiple magnetic phases, with potential implications for magnetic sensor technologies.

Contribution

It reveals large MR effects in NdCoAsO and SmCoAsO due to complex magnetic phase interactions, expanding understanding of magnetic transitions in layered compounds.

Findings

Large MR observed in NdCoAsO and SmCoAsO.

MR persists up to Curie temperature in SmCoAsO.

Presence of multiple magnetic phases influences MR behavior.

Abstract

A large magnetoresistance (MR) effect was observed in the layered compounds NdCoAsO and SmCoAsO, in which ferromagnetically ordered itinerant-electrons of Co are sandwiched by localized 4$f$-electrons of $Ln^{3+}$, below ferromagnetic-antiferromagnetic transition (FAFT) temperature $T_\mathrm{N}$ as observed in other FAFT compounds. In SmCoAsO, the large MR effect is also observed up to the Curie temperature $T_\mathrm{C}$, and it is found to be originating in the presence of another antiferromagnetic phase in the low-magnetic field region of the ferromagnetic phase.