Magnetoresistance and the states of atomic valence of La-Co-Mn system oxides

• Published in: Nihon Seramikkusu Kyōkai gakujutsu ronbunshi Vol. 110; no. 3; pp. 193 - 199
• Main Authors: HOSHI, Kazushi, NAGASE, Dai, WATANABE, Koichi
• Format: Journal Article
• Language: Japanese
• Published: Tokyo Nippon seramikkusu kyokai 2002
• ISSN: 0914-5400

Magnetic and electric properties of LaCoxMn1-xO3 (x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) compounds were measured by applying the Superconducting Quantum Interference Device (SQUID) in magnetic fields of 0 and 5 tesla at low temperatures. Respective atomic valences and the fraction of Co and Mn ions were examined by XPS at room temperature. Discrepancies in the magnetoresistance of the compounds with and without an applied magnetic field decreased with an increase of Co ion, and the maximum point of each magnetoresistance vs. temperature curve corresponded with the Curie temperature of transition from paramagnetic to ferromagnetic. Judging from the values of effective magnetic moment obtained from the Curie constant and as a result of deconvolution of the XPS spectrum, it was found that Co and Mn ions in the compounds coexisted at the mixed valence states. The electron configuration of the former ion was low spin states of CoII+ and CoIII+ whereas that of the latter ion was high spin states of Mn3+ and Mn4+. It is probable that the ferromagnetic double exchange interaction between Mn3+ and Mn4+ ions dominated over that between CoII+ and CoIII+ ions. 15 refs.