Investigation of the high Curie temperature inSr2CrReO6

A detailed neutron diffraction study of ${\mathrm{Sr}}_{2}{\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Cr}}_{x}\mathrm{Re}{\mathrm{O}}_{6}$ half-metallic double perovskites has been carried out. With increasing Cr content, the temperature for the cubic-tetragonal transition decreases (${T}_{t}\ensuremath{\approx}490\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $x=0$ and $\ensuremath{\approx}260\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $x=1$) and the cell volume shrinks more than 2% while the Curie temperature increases substantially (${T}_{C}\ensuremath{\approx}420\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $x=0$ and $\ensuremath{\approx}620\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $x=1$). We discuss the origin of the anomalously high ${T}_{C}$ of ${\mathrm{Sr}}_{2}\mathrm{Cr}\mathrm{Re}{\mathrm{O}}_{6}$ in terms of structural and band hybridization effects.