Magnetic ground state, critical analysis of magnetization, and large magnetocaloric effect in the ferromagnetically coupled kagome lattice YCa$_3$(MnO)$_3$(BO$_3$)$_4$

TL;DR

This study investigates the magnetic properties, phase transitions, and magnetocaloric effect of a frustrated kagome lattice compound, revealing its potential for magnetic refrigeration due to large magnetocaloric parameters and second order transition.

Contribution

It provides a comprehensive analysis combining experiments and calculations, highlighting the compound's unconventional ferromagnetic order and large magnetocaloric effect as novel findings.

Findings

Unconventional ferromagnetic ordering at 7.8 K

Large magnetocaloric effect with ΔS_m ≈ 12 J/kg-K

Second order phase transition with no hysteresis

Abstract

We report a detailed study of the magnetic properties, critical analysis of magnetization, and magnetocaloric effect of a spin-$2$ kagome lattice YCa$_3$(MnO)$_3$(BO$_3$)$_4$. The experiments are complemented by the density functional band structure calculations. The magnetic measurements suggest a highly frustrated nature of the compound due to competing ferro- and antiferromagnetic interactions with the dominant one being ferromagnetic. It undergoes a unconventional ferromagnetic ordering at $T^* \simeq 7.8$ K and a field induced metamagnetic transition in low fields, implying spin canting. A $H$-$T$ phase diagram is constructed that features three phase regimes. Indeed, the band structure calculations reveal dominant ferromagnetic interaction along the chains that are coupled antiferromagnetically yielding a frustrated kagome geometry. This compound shows a large magnetocaloric effect with isothermal entropy change $\Delta S_{\rm m} \simeq 12$ J/kg-K, adiabatic temperature change $\Delta T_{\rm ad} \simeq 8.4$ K, and relative cooling power $RCP \simeq 349$ J/kg for a field change of 7 T. The critical analysis of magnetization and magnetocaloric parameters suggests that the transition is a second order phase transition and it is tricritical mean field type. Owing to it's large magnetocaloric parameters, second order phase transition, and no thermal hysteresis, YCa$_3$(MnO)$_3$(BO$_3$)$_4$ emerges as a potential rare-earth free material for magnetic refrigeration.