Crystal structure and magnetic ordering of novel perovskite-related barium osmate Ba11Os4O24

The crystal structure and magnetic properties of new barium osmate Ba11Os4O24 are investigated. This compound crystallizes in a cation-deficient double perovskite-related structure (space group I41/a; Z=4), which is isostructural with the strontium rhenate, Sr11Re4O24. This compound shows semiconductive behavior with thermal activation. A weak ferromagnetic transition has been found at 7.5 K through its magnetic susceptibility measurements. At 6.8 K, a λ-type specific heat anomaly has been observed.