Unusual UUDD magnetic chain structure of the spin-1/2 tetragonally distorted spinel GeCu2O4

Abstract

GeCu2O4 exhibits a tetragonal spinel structure due to the strong Jahn-Teller distortion associated with Cu2+ ions. We show that its magnetic structure can be described as slabs composed of a pair of layers with orthogonally oriented spin 1/2 Cu chains in the basal ab plane. The spins between the two layers within a slab are collinearly aligned while the spin directions of neighboring slabs are perpendicular to each other. Interestingly, we find that spins along each chain form an unusual up-up-down-down (UUDD) pattern, suggesting a non-negligible nearest-neighbor biquadratic exchange interaction in the effective classical spin Hamiltonian. We hypothesize that spin-orbit coupling and orbital mixing of Cu2+ ions in this system is non-negligible, which calls for future calculations using perturbation theory with extended Hilbert (spin and orbital) space and calculations based on density functional theory including spin-orbit coupling and looking at the global stability of the UUDD state.

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• Unified description of electronic orderings and cross correlations by complete multipole representation
• Hedgehog-lattice spin texture in classical Heisenberg antiferromagnets on the breathing pyrochlore lattice
• Putative spin-nematic phase in BaCdVO(PO${}_4$)${}_2$
• The origin of up-up-down-down magnetic order in Cu${}_2$GeO${}_4$
• Hedgehog lattice and field-induced chirality in breathing-pyrochlore Heisenberg antiferromagnets
• Elementary excitation in the spin-stripe phase in quantum chains
• Complex magnetic ground states and topological electronic phases of atomic spin chains on superconductors
• Multiferroicity in the frustrated spinel cuprate GeCu${}_2$O${}_4$
• Nearly degenerate ground states of a checkerboard antiferromagnet and their bosonic interpretation
• Stabilization of high-pressure GeCu${}_2$O${}_4$ spinel cuprate with quasi-1D $S=1/2$ chains in the epitaxial thin-film form
• Epitaxial stabilization of thin films of the frustrated Ge-based spinels
• Magnetic structures of electron systems on the extended spatially completely anisotropic triangular lattice near quantum critical points