Large magnetocaloric effect in the frustrated antiferromagnet EuIr$_2$P$_2$

TL;DR

This paper combines theoretical simulations and experimental measurements to demonstrate a significant magnetocaloric effect in the frustrated antiferromagnet EuIr$_2$P$_2$, linked to a multicritical point in its phase diagram.

Contribution

It provides the first combined theoretical and experimental analysis of the magnetocaloric effect in EuIr$_2$P$_2$, highlighting the role of frustration and multicriticality.

Findings

Maximum entropy change of 5.14 J kg$^{-1}$K$^{-1}$ at 2.45 K for 1.2 Tesla field change

Large magnetocaloric effect observed around 2.5 K in experiments

The phase diagram features a multicritical point influencing the magnetocaloric response.

Abstract

We present a theoretical analysis of the magnetocaloric effect in the frustrated antiferromagnet \Eu. Monte Carlo simulations indicate a large magnetic entropy change $\Delta S_M^{\text{max}} \sim 5.14$ J kg$^{-1}$K$^{-1}$ at $T=2.45$K for a moderate change in the external magnetic field $\Delta B=1.2$ Tesla. The highest value of $\Delta S_M$ seems to be associated with the presence of a multicritical point in the magnetic field versus temperature phase diagram (at $B_m\sim 1.2$ Tesla and $T_m\sim 2.2$ K) but it persists with similar large values for a broad range of temperatures $T\lesssim T_m$. Single crystal \Eu~magnetization vs magnetic field experiments allowed us to obtain the magnetocaloric effect for $T>2$ K. The results are consistent with the theoretical analysis and show a large magnetocaloric effect for $T\sim 2.5$ K. Finally, we present a phenomenological Landau functional analysis that provides a simplified description of the phase diagram and of the magnetocaloric effect. Although the magnetic frustration in this system leads to a rich phase diagram, we found no clear indication that it plays a significant role enhancing the magneticaloric effect, other than by reducing the transition temperatures and fields.