Inter-Cation Charge Transfer Mediated Antiferromagnetism in Co${}_{1+x}$Ir${}_{2-x}$S${}_4$

Abstract

The antiferromagnetism in transition metal compounds is mostly mediated by the bridging anions through a so-called superexchange mechanism. However, in materials like normal spinels $A{B}_2{X}_4$ with local moments only at the $A$ site, such an anion-mediated superexchange needs to be modified. Here we report a new spinel compound Co${}_{1+x}$Ir${}_{2-x}$S${}_4$ ($x$ = 0.3). The physical property measurements strongly suggest an antiferromagnetic-like transition at 292 K in the Co($A$) diamond sublattice. The first-principle calculations reveal that the nearest-neighbor Co($A$) spins align antiferromagnetically with an ordered magnetic moment of 1.67 ${\mu }_{\mathrm{B}}$, smaller than the expected $S=3/2$ for Co${}^{2+}$. In the antiferromagnetic state, there exists an inter-cation charge-transfer gap between the non-bonding Ir-$t_{2g}$ orbitals at the valence band maximum and the Co-S antibonding molecular orbitals at the conduction band minimum. The small charge transfer energy significantly enhances the virtual hopping between these two states, facilitating a robust long-range superexchange interaction between two neighboring CoS${}_4$ complexes, which accounts for the high Néel temperature in Co${}_{1+x}$Ir${}_{2-x}$S${}_4$. This inter-cation charge transfer mediated magnetic interaction expands the traditional superexchange theory, which could be applicable in complex magnetic materials with multiple cations.

arXiv comment10 pages, 7 figures

References in corpus (15)

• Stacking-Dependent Magnetism in Bilayer CrI${}_3$
• Order by disorder and spiral spin liquid in frustrated diamond lattice antiferromagnets
• Spin and orbital frustration in MnSc_2S_4 and FeSc_2S_4
• Spiral spin-liquid and the emergence of a vortex-like state in MnSc${}_2$S${}_4$
• Electronic band structure and exchange coupling constants in ACr2X4 spinels
• Itinerant ferromagnetism in half-metallic CoS_2
• Optical Absorption Induced by Small Polaron Formation in Transition Metal Oxides -- The Case of Co${}_3$O${}_4$
• Super-Exchange Theory for Polyvalent Anion Magnets
• Experimental evidence of a collinear antiferromagnetic ordering in the frustrated CoAl2O4 spinel
• Spin order and dynamics in the diamond-lattice Heisenberg antiferromagnets CuRh2O4 and CoRh2O4
• Excitation spectrum and magnetic field effects in a quantum critical spin-orbital system:FeSc${}_2$S${}_4$
• Antiferromagnetic and Orbital Ordering on a Diamond Lattice Near Quantum Criticality
• Structure, magnetic susceptibility and specific heat of the spin-orbital-liquid candidate FeSc2S4 : Influence of fe off-stoichiometry
• Magnetic order and exchange couplings in the frustrated diamond lattice antiferromagnet MnSc${}_2$Se${}_4$
• Multi-phase competition in quantum $XY$ pyrochlore antiferromagnet CdYb${}_2$Se${}_4$: zero and applied magnetic field study

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