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Structural and doping effects in the half-metallic double perovskite A2CrWO6 (A = Sr, Ba, and Ca)

Philipp, JB and Majewski, P and Alff, L and Erb, A and Gross, R and Graf, T and Brandt, MS and Simon, J and Walther, T and Mader, W and Topwal, D and Sarma, DD (2003) Structural and doping effects in the half-metallic double perovskite A2CrWO6 (A = Sr, Ba, and Ca). In: Physical Review B (Condensed Matter and Materials Physics -1(II)), 68 . 144431-1-13.

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Abstract

The structural, transport, magnetic, and optical properties of the double perovskite A2CrWO6 with A = Sr,Ba,Ca have been studied. By varying the alkaline earth ion on the A site, the influence of steric effects on the Curie temperature TC and the saturation magnetization has been determined. A maximum TC = 458 K was found for Sr2CrWO6 having an almost undistorted perovskite structure with a tolerance factor f~1. For Ca2CrWO6 and Ba2CrWO6 structural changes result in a strong reduction of TC. Our study strongly suggests that for the double perovskites in general an optimum TC is achieved only for f~1, that is, for an undistorted perovskite structure. Electron doping in Sr2CrWO6 by a partial substitution of Sr2+ by La3+ was found to reduce both TC and the saturation magnetization Ms. The reduction of Ms could be attributed both to band structure effects and the Cr/W antisites induced by doping. Band structure calculations for Sr2CrWO6 predict an energy gap in the spin-up band, but a finite density of states for the spin-down band. The predictions of the band structure calculation are consistent with our optical measurements. Our experimental results support the presence of a kinetic energy driven mechanism in A2CrWO6, where ferromagnetism is stabilized by a hybridization of states of the nonmagnetic W site positioned in between the high spin Cr sites.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to American Physical Society (APS)
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 25 Aug 2004
Last Modified: 19 Sep 2010 04:14
URI: http://eprints.iisc.ernet.in/id/eprint/1332

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