A rocksalt-structure high entropy oxide (AlCrFeNiMn)O film with room-temperature ferromagnetism

Rocksalt-structure high entropy oxides (HEOs) usually exhibit antiferromagnetic ordering characteristics. Here, we report for the first time the ferromagnetic order of a rocksalt-structure (AlCrFeNiMn)O high entropy oxide (RA-HEO), whose saturation magnetization reaches 164 emu/cm³ at room temperature, despite substantial chemical disorders. The rocksalt-structure HEOs exhibit ferromagnetic order only when their magnetic cations contain both the unoccupied $e_g$ orbitals and half-filled $e_g$ orbitals. Our works give fundamental insight into the role of the orbital state of magnetic cations and associated superexchange mechanism in rocksalt-structure HEOs.