High‐pressure synthesis, crystal structure, and magnetic property of LaCo6O11

Abstract

AbstractA novel cobalt oxide LaCo6O11 has been synthesized under high pressure of 8 GPa, and its crystal structure and magnetic property have been investigated. Rietveld analysis using synchrotron X‐ray powder diffraction data demonstrates that LaCo6O11 crystallizes in the magnetoplumbite‐derived structure as well as A2+Co6O11 (A = Ca, Sr, Ba). Bond valence sum (BVS) calculation exhibits a substantial decrease in BVS of octahedral Co sites with itinerant electrons, whereas BVS at trigonal bipyramidal Co site with localized electrons is unchanged, indicating that the doped electrons are predominantly injected into the Co sites with electric conductivity. Magnetization measurement shows that the magnetic ground state of LaCo6O11 is similar to the antiferromagnetic‐like one in CaCo6O11. However, the absence of a field‐induced ferrimagnetic transition in LaCo6O11 indicates the robustness of the antiferromagnetic‐like ground state. The difference in the magnetic state under the external magnetic field between LaCo6O11 and CaCo6O11 is attributed to the suppression of the ferromagnetic RKKY interaction because of the reduction in hole carrier density by La3+ substitution for Ca2+.