Charge-transfer driven ferromagnetism in a disordered three-dimensional 3d-5d spin system

Abstract A three-dimensional disordered spin system consisting of 3d transition metal ion Mn4+ with strong electronic correlations and heavy 5d transition metal ion Ir4+ has been investigated in form of a perovskite thin film. The studied compound of the composition SrMn0.5Ir0.5O3 does not exist as bulk or single crystal, but can be stabilized by epitaxy onto SrTiO3 single crystals as fully disordered double perovskite by pulsed laser deposition. As measured by X-ray circular dichroism, the ground state of this material is ferromagnetic with both, Mn and Ir, spins aligned in parallel. This unusual ground state can be qualitatively explained by charge-transfer driven magnetic exchange involving Mn eg-state and Ir t2g-state, with no evidence of spin–orbit coupling in Ir. Due to the coexistence of competing magnetic interactions and randomness in the system, spin-glass features are observed at low temperatures.