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

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 $T^{\ast }\simeq 7.8$ 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 $\hat{I}”S_{\mathrm{m}}\simeq 12$ J/kg-K, adiabatic temperature change $\hat{I}”T_{\mathrm{ad}}\simeq 8.4$ 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.

14 pages, 11 figures