  Room-temperature ferrimagnetism was discovered for the anti-site-disordered
perovskite Ca2MnOsO6 with Tc = 305 K. Ca2MnOsO6 crystallizes into an
orthorhombic structure with a space group of Pnma, in which Mn and Os share the
oxygen-coordinated-octahedral site at an equal ratio without a noticeable
ordered arrangement. The material is electrically semiconducting with
variable-range-hopping behavior. X-ray absorption spectroscopy confirmed the
trivalent state of the Mn and the pentavalent state of the Os. X-ray magnetic
circular dichroism spectroscopy reveals that the Mn and Os magnetic moments are
aligned antiferromagnetically, thereby classifying the material as a
ferrimagnet which is in accordance with band structure calculations. It is
intriguing that the magnetic signal of the Os is very weak, and that the
observed total magnetic moment is primarily due to the Mn. The Tc = 305 K is
the second highest in the material category of so-called disordered
ferromagnets such as CaRu1-xMnxO3, SrRu1-xCrxO3, and CaIr1-xMnxO3, and hence,
may support the development of spintronic oxides with relaxed requirements
concerning the anti-site disorder of the magnetic ions.
