Magnetocaloric effect in kagome MgMn6Sn6

Abstract

We have studied magnetocaloric effect of kagome MgMn₆Sn₆ single crystal. The MgMn₆Sn₆ single crystal exhibits a typical transition of ferromagnetic (FM) to paramagnetic (PM). Maximum magnetic entropy change ($-\Delta S_M^{\max }$) and relative cooling power (RCP) for a field change of 0–50 kOe were calculated to be 3.05 J/kg K and 129 J/kg for H//ab, 2.76 J/kg K and 115 J/kg for H//c, respectively. Concurrently, around the phase transition temperature T_C, the scaling approach for MgMn₆Sn₆ is used to study the magnetic entropy change $\left[\Delta S_M\left(T,H\right)\right]$. The outcome suggests that, in the presence of high field, the curves of $\Delta S_M\left(T,H\right)$ can be effectively combined to form a single, universal curve that is unaffected by temperature or external fields. Nevertheless, under low field, $\Delta S_M\left(T,H\right)$ curves diverge slightly below T_C, indicating a first-order transition feature. According to the scaling analysis of $\Delta S_M\left(T,H\right)$ curves, the phase transition of MgMn₆Sn₆ is forced into a second-order one under high field conditions, even if in the low field zone, it is a weak first-order type. Furthermore, it is discovered that the observed magnetocaloric effect (MCE) in kagome MgMn₆Sn₆ could not be satisfactorily explained by a basic theoretical model that simply took into consideration the magnetoelastic and magneto electron coupling.