Rare earth magnetism in CeFeAsO: A single crystal study

Abstract

Single crystals of CeFeAsO, large enough to study the anisotropy of the magnetic properties, were grown by an optimized Sn-flux technique. The high quality of our single crystals is apparent from the highest residual resistivity ratio (RRR) ≈ 12, reported among undoped RFeAsO compounds (R = rare earth) as well as sharp anomalies in resistivity, specific heat, C(T ), and thermal expansion at the different phase transitions. The magnetic susceptibility χ(T ) presents a large easy-plane anisotropy consistent with the lowest crystal electric field doublet having a dominant 06 character. Curie-Weiss-like susceptibilities for magnetic field parallel and perpendicular to the crystallographic c-axis do not reveal an influence of a staggered field on the Ce site induced by magnetic ordering of the Fe. Furthermore, the standard signatures for antiferromagnetic order of Ce at TN4f = 3.7K observed in χ(T ) and C(T ) are incompatible with a Zeeman splitting △ ≈ 10K of the CEF ground state doublet at low temperature due to the Fe-magnetic order as previously proposed. Our results can be reconciled with the earlier observation by assuming a comparatively stronger effect of the Ce-Ce exchange leading to a reduction of this Zeeman splitting below 15 K. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.