The ac-magnetic susceptibility and dielectric response of complex spin ordering processes in Mn3O4

We report a meticulous study of the ac-magnetization dynamics (χac(T)), relative dielectric permittivity er(T), and magneto-dielectric (Δer/er(H)) response of various complex magnetic transitions that occur below the ferrimagnetic Neel temperature TN of Mn3O4. Besides the known sequence of transitions at TN ∼ 42.75 K, T1 ∼ 39 K, and T2 ∼ 34 K, the existence of a new anomaly reported recently at 38 K (T*) has been successfully probed by χac(T) and er(T) measurements. The effect of external dc-bias fields (HDC) and driving frequency (f) on the above mentioned transitions has been investigated in consonance with the er(T) and Δer/er(T,H) results. For the first time, we observed a clear hysteresis of about 5.15 K in the zero-field er(T) across the incommensurate-to-commensurate transition T2 ∼ 34 K, which provides evidence to the first-order nature of this transition. The Arrott plot (H/M vs. M2) criterion has been used to distinguish the nature of all the sequential transitions that take place below TN.