Theory of High T${}_c$ Ferrimagnetism in a Multi-orbital Mott Insulator

Abstract

We propose a model for the multi-orbital material Sr${}_2$CrOsO${}_6$ (SCOO), an insulator with remarkable magnetic properties and the highest $T_c\simeq 725$ K among {\em all} perovskites with a net moment. We derive a new criterion for the Mott transition $({\tilde{U}}_1{\tilde{U}}_2{)}^{1/2}>2.5W$ using slave rotor mean field theory, where $W$ is the bandwidth and ${\tilde{U}}_{1(2)}$ are the effective Coulomb interactions on Cr(Os) including Hund's coupling. We show that SCOO is a Mott insulator, where the large Cr ${\tilde{U}}_1$ compensates for the small Os ${\tilde{U}}_2$. The spin sector is described by a frustrated antiferromagnetic Heisenberg model that naturally explains the net moment arising from canting and also the observed non-monotonic magnetization $M(T)$. We predict characteristic magnetic structure factor peaks that can be probed by neutron experiments.

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Cited by in corpus (8)

• Theory of Half-Metallic Double Perovskites I: Double Exchange Mechanism
• Magnetic order and electronic structure of 5d3 double perovskite Sr2ScOsO6
• Ferrimagnetism in the double perovskite Ca2FeOsO6: a density functional study
• Theory of Half-Metallic Double Perovskites II: Effective Spin Hamiltonian and Disorder Effects
• J-freezing and Hund's rules in spin-orbit-coupled multiorbital Hubbard models
• Long-range magnetic interaction and frustration in double perovskite Sr${}_2$NiIrO${}_6$
• Microscopic origin of pressure-induced isosymmetric transitions in fluoromanganate cryolites
• From Frustrated to Unfrustrated: Coupling two triangular-lattice itinerant Quantum Magnets