Thermally induced variable-range-hopping crossover and ferromagnetism in the layered cobalt oxide Sr{sub 2}Y{sub 0.5}Ca{sub 0.5}Co{sub 2}O{sub 7}
Temperature-dependent transport and magnetic measurements on Sr{sub 2}Y{sub 0.5}Ca{sub 0.5}Co{sub 2}O{sub 7} indicate that ferromagnetism appears along with a crossover between two forms of variable-range-hopping (VRH) conductivity on cooling. Efros-Shklovskii (ES)-type VRH conduction was found below approximately 30 K, transformed from Mott-type VRH at higher temperature. The magnitude of the Coulomb gap and the Mott-ES VRH crossover temperature are {approx}57 K and {approx}170 K, respectively. These are unusually large compared to those of nonmagnetic disordered materials. The peculiar electronic state for the ferromagnetic Coulomb gap is probably due to Coulomb correlations among d electrons in the disordered system.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40205552
- Journal Information:
- Physical Review B, Vol. 63, Issue 6; Other Information: DOI: 10.1103/PhysRevB.63.064401; Othernumber: PRBMDO000063000006064401000001; 001106PRB; PBD: 1 Feb 2001; ISSN 0163-1829
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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