Theory of dilution effect in orbital ordered system is presented. The eg 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 eg orbital model without spin degree of freedom, reduction in 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 in this interaction around vacant sites bring about this phenomenon. Present results explain the recent experiments in transition-metal compounds with orbital dilution.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2009 Jan 5|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics