RESUMEN
A cubic quadruple perovskite oxide CeMn3Cr4O12 has been synthesized under high-pressure and high-temperature conditions of 8 GPa and 1273 K. The X-ray absorption spectroscopy reveals that the Ce ions are in a trivalent state, as represented by the ionic model of Ce3+Mn3+3Cr3+4O12. The magnetic study demonstrates three independent antiferromagnetic transitions attributed to Ce (â¼10 K), Mn (46 K), and Cr (133 K) ions. Furthermore, a magnetic field-induced antiferromagnetic-to-ferromagnetic (metamagnetic) transition of Ce3+ 4f moments is observed at low temperatures below 20 K, exhibiting a rare example of metamagnetism in the Ce3+-oxides. This finding represents that the 3d-electron magnetic sublattices play a role in the metamagnetism of 4f-electron magnetic moments, demonstrating a new aspect of the 3d-4f complex electron systems.
RESUMEN
A novel quadruple perovskite oxide CeCu3Co4O12 has been synthesized in high-pressure and high-temperature conditions of 12 GPa and 1273 K. Rietveld refinement of the synchrotron X-ray powder diffraction pattern reveals that this oxide crystallizes in a cubic quadruple perovskite structure with the 1:3-type ordering of Ce and Cu ions at the A-site. X-ray absorption spectroscopy analysis demonstrates the valence-state transitions in the ACu3Co4O12 series (A = Ca, Y, Ce) from Ca2+Cu3+3Co3.25+4O12 to Y3+Cu3+3Co3+4O12 to Ce4+Cu2.67+3Co3+4O12, where the electrons are doped in the order from B-site (Co3.25+ â Co3+) to A'-site (Cu3+ â Cu2.67+). This electron-doping sequence is in stark contrast to the typical B-site electron doping for simple ABO3-type perovskite and quadruple perovskites CaCu3B4O12 (B = V, Cr, Mn), further differing from the monotonical A'-site electron doping for Na1-xLaxMn3Ti4O12 and A'- and B-site electron doping for AMn3V4O12 (A = Na, Ca, La). The differences in the electron-doping sequences are interpreted by rigid-band models, proposing a wide variety of electronic states for the complex transition-metal oxides containing the multiple valence-variable ions.