Magnetic couplings in edge-sharing high-spin d ⁷ compounds

Abstract

High-spin d7 Co(II) compounds have recently been identified as possible platforms for realising highly anisotropic and bond-dependent couplings featured in quantum-compass models such as the celebrated Kitaev model. In order to evaluate this potential, we consider all symmetry-allowed contributions to the magnetic exchange for ideal edge-sharing bonds. Though a combination of ab-initio and cluster many-body calculations we conclude that bond-dependent couplings are generally suppressed in favor of Heisenberg exchange for real materials. Consequences for several prominent materials including Na2Co2TeO6 and BaCo2(AsO4)2 are discussed.

Geometrical frustration versus Kitaev interactions in BaCo 2 (AsO 4 ) 2

“…While writing this paper, we became aware of three ab initio theoretical investigations of BCAO. Two of them ( 71 , 72 ) corroborate our conclusion regarding the nature of magnetic interaction in BCAO and propose a coherent microscopic theory for it. Another ( 73 ) observes the formation of spin–orbit-entangled J eff = 1/2 moments that could potentially support the claim of Kitaev physics.…”

Machine learning facilitated by microscopic features for discovery of novel magnetic double perovskites

“…These microscopic parameters underlie the electronic and magnetic properties, but quantitative information on the magnetic properties can be obtained using analytical or perturbative expressions that are available for several specic cases only. 9,36,37 Machine learning methods can be an appealing alternative to such analytical approaches, because of its potential to capture the elusive, yet inherent link between the transfer integrals and physical observables.…”

Beyond Kitaev physics in strong spin-orbit coupled magnets

“…Similarly, for the d 7 cobaltates, theoretical studies suggest that, despite a weaker SOC (compared to their 4d and 5d counterparts), the bond-anisotropic K and Γ interactions can be realized in materials when the direct intraorbital t 2g -t 2g hopping (t 3 ) is negligible compared to indirect hoppings [80][81][82]. While this is true for some cobaltates, it has recently been pointed out that t 3 is the largest hopping integral in BaCo 2 (XO 4 ) 2 with X = As, P leading to the dominant Heisenberg interaction [124,[127][128][129]. Further studies are currently underway to identify cobaltates with dominant Kitaev interaction.…”