Structural and doping effects in the half-metallic double perovskite $A_2$CrWO$_6$

J. B. Philipp; P. Majewski; L. Alff; A. Erb; R. Gross; T. Graf; M. S. Brandt; J. Simon; T. Walther; W. Mader; D. Topwal; D. D. Sarma

doi:10.1103/PhysRevB.68.144431

paper

Structural and doping effects in the half-metallic double perovskite $A_{2}$ CrWO $_{6}$

arXiv:cond-mat/0306357 · doi:10.1103/PhysRevB.68.144431

Abstract

he structural, transport, magnetic and optical properties of the double perovskite $A_{2}$ CrWO $_{6}$ 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 $T_{C}$ and the saturation magnetization has been determined. A maximum $T_{C} = 458$ K was found for Sr $_{2}$ CrWO $_{6}$ having an almost undistorted perovskite structure with a tolerance factor $f ≃ 1$ . For Ca $_{2}$ CrWO $_{6}$ and Ba $_{2}$ CrWO $_{6}$ structural changes result in a strong reduction of $T_{C}$ . Our study strongly suggests that for the double perovskites in general an optimum $T_{C}$ is achieved only for $f ≃ 1$ , that is, for an undistorted perovskite structure. Electron doping in Sr $_{2}$ CrWO $_{6}$ by a partial substitution of Sr $^{2 +}$ by La $^{3 +}$ was found to reduce both $T_{C}$ and the saturation magnetization $M_{s}$ . The reduction of $M_{s}$ could be attributed both to band structure effects and the Cr/W antisites induced by doping. Band structure calculations for Sr $_{2}$ CrWO $_{6}$ 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 $A_{2}$ CrWO $_{6}$ , where ferromagnetism is stabilized by a hybridization of states of the nonmagnetic W-site positioned in between the high spin Cr-sites.

14 pages, 10 figures

Structural and doping effects in the half-metallic double perovskite $A_{2}$ CrWO $_{6}$

Abstract

References in corpus (11)

Cited by in corpus (42)

Structural and doping effects in the half-metallic double perovskite A2​CrWO6​

Abstract

References in corpus (11)

Cited by in corpus (42)

Structural and doping effects in the half-metallic double perovskite $A_{2}$ CrWO $_{6}$