Theory of High Tc Ferrimagnetism in a Multiorbital Mott Insulator

We propose a model for the multiorbital material Sr2CrOsO6, an insulator with remarkable magnetic properties and the highest T-c similar or equal to 725 K among all perovskites with a net moment. We derive a new criterion for the Mott transition ((U) over tilde (1)(U) over tilde (2))(1/2) 2 > 2.5W by using slave-rotor mean field theory, where W is the bandwidth and (U) over tilde (1(2)) are the effective Coulomb interactions on Cr( Os) including Hund's coupling. We show that Sr2CrOsO6 is a Mott insulator, where the large Cr (U) over tilde (1) compensates for the small Os (U) over tilde (2). The spin sector is described by a frustrated antiferromagnetic Heisenberg model that naturally explains the net moment arising from canting and also the observed nonmonotonic magnetization M(T). We predict characteristic magnetic structure factor peaks that can be probed by neutron experiments. DOI: 10.1103/PhysRevLett.110.087203