Reversed Crystal-Field Splitting and Spin-Orbital Ordering in $\alpha$-Sr${}_2$CrO${}_4$

Abstract

The origin of successive phase transitions observed in the layered perovskite $\alpha$-Sr${}_2$CrO${}_4$ is studied by the density-functional-theory-based electronic structure calculation and mean-field analysis of the proposed low-energy effective model. We find that, despite the fact that the CrO${}_6$ octahedron is elongated along the $c$-axis of the crystal structure, the crystal-field level of nondegenerate $3d_{xy}$ orbitals of the Cr ion is lower in energy than that of doubly degenerate $3d_{yz}$ and $3d_{xz}$ orbitals, giving rise to the orbital degrees of freedom in the system with a $3d^2$ electron configuration. We show that the higher (lower) temperature phase transition is caused by the ordering of the orbital (spin) degrees of freedom.

5 pages, 5 figures; J. Phys. Soc. Jpn., in press

References in corpus (3)

• Electronic Structure of Strongly Correlated Systems Emerging from Combining Path-Integral Renormalization Group with Density Functional Approach
• Peierls Mechanism of the Metal-Insulator Transition in Ferromagnetic Hollandite K2Cr8O16
• K${}_2$Cr${}_8$O${}_{16}$ predicted as a half-metallic ferromagnet: Scenario for a metal-insulator transition

Cited by in corpus (7)

• Origin of the Magnetic and Orbital ordering in $\alpha$-Sr${}_2$CrO${}_4$
• Orbital ordering in the layered perovskite material CsVF${}_4$
• (Anti-)Altermagnetism from Orbital Ordering in the Ruddlesden-Popper Chromates Sr${}_{n+1}$Cr${}_n$O${}_{3n+1}$
• Spin-orbit coupling induced orbital entanglement in a three-band Hubbard model
• Flavor Nernst effects in quantum paramagnets
• Pressure-Induced Restoration of the Reversed Crystal-Field Splitting in $\alpha$-Sr${}_2$CrO${}_4$
• Effect of spin-orbit coupling on spin and orbital ordering in Sr${}_{n+1}$Cr${}_n$O${}_{3n+1}$, $n=1,2$