Hidden magnetism, nonlinear magnetodielectric coupling, and large multicaloric effect in multiferroic L -type Fe2 (Mo O4)3

Fe2(MoO4)3 is a well-established L-type ferrimagnetic (L-FIM) material with field-induced magnetic ordering (TN2) and multiferroic properties below TN1 (around 12 K). In this study, we investigate the magnetic properties of Fe2(MoO4)3 through temperature- and field-dependent ac and dc magnetic susceptibility χ(T) measurements. Isothermal magnetization data reveal an additional metamagnetic transition (HC2) beyond the existing boundary between L-FIM and multiferroic phases (HC1). Frequency-dependent ac magnetic susceptibility data demonstrate reentrant-spin-glass-like behavior below TN1, with a critical temperature (Tg0) of 6.2 K. Notably, a nonlinear magnetodielectric response and concurrent anomalies in M(H) at the two metamagnetic transitions (HC1 and HC2) allude to a profoundly intertwined magnetoelectric (ME) nature. A finite nonlinear ME effect (αME) of about 0.56 ps/m is comparable to that of ME materials such as NdCrTiO5 and MnGa2O4. The temperature-dependent adiabatic temperature change (ΔTm) due to the contribution of magnetic spin entropy exhibits a small value (approximately 0.8 K) with an oscillatory-like magnetocaloric effect. Remarkably, the adiabatic temperature change (ΔTME) owing to magnetoelectric coupling is quite large (5.2 K under a 7 T magnetic field) near TN2. The tunability of TN2 with temperature and magnetic field strength represents a unique multicaloric medium whose temperature and field parameters can be easily adjusted for potential cryogenic applications near liquid-helium temperatures.