Spin state of the Co³⁺ion in RCoO₃compounds with the GdFeO₃structure

Abstract

X-ray-excited Co 2p photoemission lines from YCoO3, HoCoO3, GdCoO3 and Sr2(SbCo)O6 are broadened asymmetrically by multiplet splitting. The spectrum from the high-spin compound Sr2(SbCo)O6 is independent of temperature. In the other three cases the line broadening shows a marked increase with increasing temperature. This effect is attributed to a decrease, caused by thermal expansion, in the value of the octahedral ligand-field splitting parameter 10Dq, which lies not far above the value at which crossover to the high-spin state occurs. Magnetic susceptibility data for YCoO3 are shown to be consistent with this interpretation. There is no evidence in favour of an ordering transition, or of electron transfer between high-spin and low-spin Co3+ ions.

Experimental phase diagram determination and thermodynamic assessment of the Gd2O3–CoO system

“…In the rare-earth cobaltite ACoO 3 (A = La, Pr, Sm, Nd, Eu, Gd) perovskites, only the existence of bivalent and trivalent Co-ions has been confirmed experimentally [27][28][29][30]. Thus the formula (Gd 3+ ) (Co 3+ , Co 2+ ) (O 2À , Va) 3 is used for the description of GdCoO 3Àd , whereby each bracket refers to one crystal sublattice of the general perovskite structure ABO 3 .…”