Competing interaction driven broad magnetic entropy distribution in triangular net compounds \text{Ba$_3$RE(BO$_3$)$_3$}, RE= Dy and Ho

Abstract

Triangular magnetic lattices have attracted significant attention as a model platform for exploring frustrated magnetism and quantum spin liquids, particularly in rare-earth-based systems. These materials also hold considerable promise for cryogenic magnetic refrigeration. In this work, we investigate the magnetic and magnetocaloric properties of the rare-earth (RE) based compounds $\text{Ba}_3\text{RE}(\text{BO}_3)_3$ ($\text{RE} = \text{Dy}$ and $\text{Ho}$). Polycrystalline samples synthesized via a solid-state reaction method crystallize in a hexagonal structure with the space group $P6_3mc$, featuring triangular nets separated by approximately $8.8~\textÅ$ along the $c$-axis. Detailed magnetic investigation reveals a deviation from pure paramagnetic behavior at low temperatures ($T < 20\text{ K}$). This is further corroborated by isothermal magnetization measurements, which exhibit non-overlapping $M$ vs. $H/T$ plots and reduced magnetization moments, suggesting significant crystal electric field (CEF) splitting of localized $f$-states. For an applied magnetic field change of $70\text{ kOe}$, the maximum entropy change (Relative Cooling Power) reaches $4.2\text{ J kg}^{-1}\text{ K}^{-1}$ ($204\text{ J kg}^{-1}$) and $7.3\text{ J kg}^{-1}\text{ K}^{-1}$ ($230\text{ J kg}^{-1}$) for the Dy- and Ho-based compounds, respectively. Overall, the positive slopes of Arrott plots, the universal scaling behaviour of $ΔS_{\text{m}}/ΔS_{\text{m}}^{\text{max}}$ versus reduced temperature ($t$), and the field exponent $c$ of the RCP versus $H$ curves indicate a second-order nature of entropy distribution, making them promising candidates for magnetocalorics in the millikelvin range.