Interplay of spin and orbital ordering in a frustrated spinel chromite

Geometric Spin Frustration, when sufficiently strong, provides a platform for novel spin textures with emergent phenomena, such as ferroelectricity. This article investigates NiCr2O4, a spinel chromite co-hosting the frustration of Cr3+ spins with orbital frustration of Ni2+ ions, with the latter expected to eradicate the spin frustration by lowering lattice symmetry. Detailed experiments unveil an intriguing reentrant-spin-glass-like behavior alongside the previously known canted ferrimagnetism. Our analysis focuses on the ordering of Cr3+ spins at two distinct sublattices, with one contributing to canted ferrimagnetism, while the other exhibits a local up arrow up arrow down arrow down arrow (spin-frustrated) texture, potentially inducing spin-glass behavior. Density functional theory calculations corroborate the experimental findings, establishing up arrow up arrow down arrow down arrow as the ground state of NiCr2O4. This study presents new prospects for ferroelectricity driven by exchange striction in orbitally ordered spinel chromites.