Dilution effect in correlated electron system with orbital degeneracy

Abstract

Theory of dilution effect in orbital ordered system is presented. The $e_g$ orbital model without spin degree of freedom and the spin-orbital coupled model in a three-dimensional simple-cubic lattice are analyzed by the Monte-Carlo simulation and the cluster expansion method. In the $e_g$ orbital model without spin degree of freedom, reduction of the orbital ordering temperature due to dilution is steeper than that in the dilute magnet. This is attributed to a modification of the orbital wave-function around vacant sites. In the spin-orbital coupled model, it is found that magnetic structure is changed from the A-type antiferromagnetic order into the ferromagnetic one. Orbital dependent exchange interaction and a sign change of this interaction around vacant sites bring about this novel phenomena. Present results explain the recent experiments in transition-metal compounds with orbital dilution.

12 pages, 16 figures

References in corpus (5)

• Competing Orders and Disorder-induced Insulator to Metal Transition in Manganites
• Orbital order in classical models of transition-metal compounds
• Dilution Effects in Two-dimensional Quantum Orbital System
• Orbital order driven quantum criticality
• Combined Effect of Bond- and Potential-Disorder in Half-Doped Manganites