Sr{sub 2/3}Y{sub 1/3}CoO{sub 8/3+{delta}}: Transition from insulating antiferromagnet to metallic ferromagnet by control of the oxygen content
- Laboratoire CRISMAT, UMR 6508 CNRS ISMRA, 6 bd Marechal Juin, FR-14050 Caen Cedex 4 (France)
Magnetic and electronic properties of the oxygen deficient ordered perovskite, Sr{sub 2/3}Y{sub 1/3}CoO{sub 8/3+{delta}}, have been studied for two different oxygen contents corresponding to {delta}=0.00 and 0.04 in the chemical formula. For the former, at low temperature, the background state is antiferromagnetic insulating (T{sub N}=290K,{rho}{sub 10K}=4x10{sup 5}{omega}cm) as expected from the presence of trivalent cobalt in the high spin-state. Remarkably, the more oxidized compound with a cobalt oxidation state of {approx}3.08 is a ferromagnetic half-metal with T{sub C}=225K and {rho}{sub 10K}=2x10{sup -3}{omega}cm. Consistently, upon application of an external magnetic field, the spin-scattering reduction in the T{sub C} vicinity is responsible for a weak negative magnetoresistance. These dramatic changes of the physical properties for such a slight increase of the cobalt oxidation state are interpreted as a result of the structural disordering created by the extra oxygens. The thermoelectric power measurements, showing a sign change of the Seebeck coefficient as the oxygen content increases, indicate that electrons moving in a metallic e{sub g} band dominate the transport properties of the ferromagnetic and metallic compound. This suggests the existence of an orbital ordering in the pristine compound, related to an ordered array of CoO{sub 4} tetrahedra, which can be collapsed by the presence of these extra oxygen anions.
- OSTI ID:
- 20725846
- Journal Information:
- Journal of Solid State Chemistry, Vol. 178, Issue 3; Other Information: DOI: 10.1016/j.jssc.2004.12.014; PII: S0022-4596(04)00659-0; Copyright (c) 2004 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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