Field-Induced Structural Transition in the Bond Frustrated Spinel ZnCr₂Se₄

The effect of an external magnetic field on the structural and magnetic properties of bond frustrated ZnCr₂Se₄ at low temperatures is investigated using magnetization, dielectric constants and thermal conductivity experiments. With an increase in the magnetic field H, the antiferromagnetic transition temperature T_N is observed to shift progressively toward lower temperatures. The corresponding high temperature cubic (Fd3m) to low temperature tetragonal (I4₁amd) structural transition is tuned simultaneously due to the inherent strong spin-lattice coupling. In the antiferromagnetic phase, an anomaly at H_C2 defined as a steep downward peak in the derivative of the M–H curve is clearly drawn. It is found that T_N versus H and H_C2 versus T exhibit a consistent tendency, indicative of a field-induced tetragonal (I4₁amd) to cubic (Fd3m) structural transition. The transition is further substantiated by the field-dependent dielectric constant and thermal conductivity measurements. We modify the T–H phase diagram, highlighting the coexistence of the paramagnetic state and ferromagnetic clusters between 100 K and T_N.