Magnetic and structural properties of the double-perovskite Ca2FeReO6

We suceeded in the preparation of polycrystalline Ca2FeReO6 which has a Curie temperature TC of 540 K, the highest value of all magnetic perovskites investigated till now. This material has been characterised by X-ray and neutron powder diffraction. We found at 548 K, a monoclinic unit cell (space group P21/n) with a=5.4366(5) Å, b=5.5393(5) Å, c=7.7344(5) Å, and β=90.044(4)°. For temperatures below 400 K, a phase separation in two monoclinic phases with identical cell volume is observed in neutron scattering. The two phases possess different magnetic structure and coercivity. The conductivity is thermally activated for all temperatures and no significant magnetoresistivity is observed.