Magnetic state of pyrochlore Cd2Os2O7 emerging from strong competition of ligand distortions and longer-range crystalline anisotropy

Abstract

By many-body quantum-chemical calculations, we investigate the role of two structural effects - local ligand distortions and the anisotropic Cd-ion coordination - on the magnetic state of Cd2Os2O7, a spin S=3/2 pyrochlore. We find that these effects strongly compete, rendering the magnetic interactions and ordering crucially depend on these geometrical features. Without trigonal distortions a large easy-plane magnetic anisotropy develops. Their presence, however, reverses the sign of the zero-field splitting and causes a large easy-axis anisotropy (D = -6.8 meV), which in conjunction with the antiferromagnetic exchange interaction (J = 6.4 meV) stabilizes an all-in/all-out magnetic order. The competition uncovered here is a generic feature of pyrochlore magnets.

5 pages, 3 figures, 5 pages supplementary material included, to appear in PRL

References in corpus (5)

• Crystal field splitting and correlation effect on the electronic structure of A2IrO3
• Magnetically driven metal-insulator transition in NaOsO3
• Tetrahedral Magnetic Order and the Metal-Insulator Transition in the Pyrochlore Lattice of Cd2Os2O7
• Testing the validity of the strong spin-orbit-coupling limit for octahedrally coordinated iridates in a model system Sr${}_3$CuIrO${}_6$
• Ab initio determination of excitation energies and magnetic couplings in correlated, quasi two-dimensional iridates

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• Covalency and vibronic couplings make a nonmagnetic j=3/2 ion magnetic
• Lattice frustration in spin-orbit Mott insulator Sr3Ir2O7 at high pressure
• Colossal enhancement of electrical conductivity in Y2Ir2O7 nanoparticles
• Role of Square Planar Coordination in the Magnetic Properties of Na4IrO4
• Energy scales in 4f1 delafossite magnets: crystal-field splittings larger than the strength of spin-orbit coupling in KCeO2
• Ultrafast dynamics in the Lifshitz-type 5$d$ pyrochlore antiferromagnet Cd${}_2$Os${}_2$O${}_7$
• Pyrochlore Oxide Hg2Os2O7 on Verge of Metal-Insulator Boundary
• Coupled Spin-Charge-Phonon Fluctuation in the All-In/All-Out Antiferromagnet Cd${}_2$Os${}_2$O${}_7$