Magnetocrystalline interactions in spinel MnCr₂O₄ single crystal probed by electron spin resonance

In this work we present a detailed magnetization, electron spin resonance (ESR) and specific capacity study on spinel MnCr₂O₄ single crystals in an extended temperature range of 5–300 K. The field-induced effect of the magnetization indicates the strong spin-lattice coupling in MnCr₂O₄ single crystal. The following results are obtained by the ESR investigation: (i) Below 35 K, since the spiral spin order, a driving force of the multiferroic (MF) effect, becomes obvious, the line shape of ESR shows asymmetric characters and the ferromagnetic resonance (FMR) model of Smit and Beljers formulation is invalid; (ii) The temperature dependence of Gilbert damping parameter α, reflecting the strength of the spin-lattice coupling, shows an abnormal behavior due to the local lattice distortion in MnCr₂O₄ single crystal. And the distortion is a triggering force for the formation of spiral spin order. Moreover, our research helps to understand the origin of the MF effect in MnCr₂O₄.