Magnetic phase transitions in SmCoAsO

Abstract

Magnetization, x-ray diffraction, and specific-heat measurements reveal that SmCoAsO undergoes three magnetic phase transitions. A ferromagnetic transition attributed to the Co ions, emerges at ${T}_{C}=57\text{ }\text{K}$ with a small saturation moment of $\ensuremath{\sim}0.15\text{ }{\ensuremath{\mu}}_{B}/\text{Co}$. Reorientation of the Co moment to an antiferromagnetic state is obtained at ${T}_{N2}=45\text{ }\text{K}$. The relative high paramagnetic effective moment ${P}_{\text{eff}}=1.57\text{ }{\ensuremath{\mu}}_{B}/\text{Co}$ indicates an itinerant ferromagnetic state of the Co sublattice. The third magnetic transition at ${T}_{N1}=5\text{ }\text{K}$ is observed clearly in the specific-heat study only. Both magnetic and $^{57}\text{F}\text{e}$ Mossbauer studies show that substitution of small quantities of Fe for Co was unsuccessful.