Coupling between phonon and short-range spin correlations in frustrated spinel LiFeCr₄O₈

Spin–phonon coupling is important in chromate spinel oxides ACr₂O₄, but its role in LiFeCr₄O₈ is not well understood. In this paper, we employ Raman scattering and first-principles phonon calculations to study this material. Ten out of 13 Raman-active modes are well assigned. Notably, no phonon splitting is observed across the structural phase transition due to the remarkably small Grüneisen constants. This observation, in conjunction with the structural data, provides compelling evidence that the structural phase transition in LiFeCr₄O₈ is primarily driven by the spin-driven Jahn–Teller effect. Interestingly, some Raman modes (at 207 cm⁻¹, 306 cm⁻¹ and 462 cm⁻¹) exhibit unusual linewidth behavior across the temperature range investigated. Furthermore, the Raman spectra in different phases show no magnetic field dependence. These results suggest that phonons couple with short-range spin correlations, offering insights into how spin and lattice degrees of freedom interact in frustrated systems.