Thermally induced variable-range-hopping crossover and ferromagnetism in the layered cobalt oxide Sr2Y0.5Ca0.5Co2O7

K. Yamaura; D. P. Young; R. J. Cava

doi:10.1103/PhysRevB.63.064401

Thermally induced variable-range-hopping crossover and ferromagnetism in the layered cobalt oxide Sr₂Y_0.5Ca_0.5Co₂O₇

K. Yamaura, D. P. Young, R. J. Cava

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Abstract

Temperature-dependent transport and magnetic measurements on Sr₂Y_0.5Ca_0.5Co₂O₇ 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 ∼57 K and ∼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.

Original language	English (US)
Journal	Physical Review B - Condensed Matter and Materials Physics
Volume	63
Issue number	6
DOIs	https://doi.org/10.1103/PhysRevB.63.064401
State	Published - Jan 10 2001

All Science Journal Classification (ASJC) codes

Electronic, Optical and Magnetic Materials
Condensed Matter Physics

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10.1103/PhysRevB.63.064401

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title = "Thermally induced variable-range-hopping crossover and ferromagnetism in the layered cobalt oxide Sr2Y0.5Ca0.5Co2O7",

abstract = "Temperature-dependent transport and magnetic measurements on Sr2Y0.5Ca0.5Co2O7 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 ∼57 K and ∼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.",

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AU - Yamaura, K.

AU - Young, D. P.

AU - Cava, R. J.

PY - 2001/1/10

Y1 - 2001/1/10

N2 - Temperature-dependent transport and magnetic measurements on Sr2Y0.5Ca0.5Co2O7 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 ∼57 K and ∼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.

AB - Temperature-dependent transport and magnetic measurements on Sr2Y0.5Ca0.5Co2O7 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 ∼57 K and ∼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.

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Thermally induced variable-range-hopping crossover and ferromagnetism in the layered cobalt oxide Sr₂Y_0.5Ca_0.5Co₂O₇

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