Magnetoelastic coupling in Sr2(Fe1−xCrx)ReO6 double perovskites

Abstract

We have investigated magnetoelastic coupling inSr2(Fe1−xCrx)ReO6 polycrystalline double perovskites. The end compound,Sr2CrReO6, shows a high ferromagnetic transition temperature of 635 K and is thought to exhibit anearly half-metallic conduction band. We probed the unexpected high orbital momentborne by the Re atom by means of volume and anisotropic magnetostriction measurementsin magnetic fields up to 12 T. Our magnetostriction results can be explained by theexistence of a large spin–orbit coupling which, in combination with crystal-field effects,produces a single-ion type magnetostrictive response. The Re orbital momenttriggers a greatly enhanced magnetocrystalline anisotropy compared to otherferromagnetic double perovskites. From our magnetostriction data, the temperaturedependence of the coercive field as a function of Cr-doping is obtained. We discoveredthat the coercive field increases as Fe is replaced with Cr, which is linked to astrong enhancement of the magnetic anisotropy. This suggests a close relationshipbetween the Fe[Cr]–O–Re coupling and the magnetic anisotropy. We also analysedthe impact of the Re orbital moment on the spin-dependent transport acrossSr2CrReO6 grain boundaries. The present work opens up the possible use of these compounds formagnetostrictive applications in a wide temperature and magnetic field range.