Giant Magnetoresistance in the Half‐Metallic Double‐Perovskite Ferrimagnet Mn₂FeReO₆

The first transition‐metal‐only double perovskite compound, Mn 2+ 2 Fe 3+ Re 5+ O 6 , with 17 unpaired d electrons displays ferrimagnetic ordering up to 520 K and a giant positive magnetoresistance of up to 220 % at 5 K and 8 T. These properties result from the ferrimagnetically coupled Fe and Re sublattice and are affected by a two‐to‐one magnetic‐structure transition of the Mn sublattice when a magnetic field is applied. Theoretical calculations indicate that the half‐metallic state can be mainly attributed to the spin polarization of the Fe and Re sites.