Orbital ordering in the ferromagnetic insulator Cs${}_2$AgF${}_4$ from first principles

Abstract

We found, using density-functional theory calculations within the generalized gradient approximation, that Cs${}_2$AgF${}_4$ is stabilized in the insulating orthorhombic phase rather than in the metallic tetragonal phase. The lattice distortion present in the orthorhombic phase corresponds to the $x^2-z^2$/$y^2-z^2$ hole-orbital ordering of the Ag${}^{2+}$ $4d^9$ ions, and this orbital ordering leads to the observed ferromagnetism, as confirmed by the present total-energy calculations. This picture holds in the presence of moderate 4d-electron correlation. The results are compared with the picture of ferromagnetism based on the metallic tetragonal phase.

5 pages, 4 figures, 1 table; a few energy/moment entries in Table I are corrected due to a proper treatment of the Ag 4s semicore state

References in corpus (1)

• Magnetism in the high-Tc analogue Cs2AgF4 studied with muon-spin relaxation