Investigation of the magnetic ground state of PrRu${}_2$Ga${}_8$ compound

Abstract

We have investigated the ground state properties of the orthorhombic structure compound PrRu${}_2$Ga${}_8$ through electronic and magnetic properties studies. The compound crystallizes in the CaCo${}_2$Al${}_8$-type structure, belonging to space group $Pbam$ (No. 55). The temperature dependence specific heat shows a $\lambda$-type anomaly at $T_N$ = 3.3 K, indicating a bulk phase transition probably of antiferromagnetic origin. At the Néel temperature $T_N$, the entropy approaches the value of 4.66~J/mol.K which is about 0.8Rln(2), where R is the universal gas constant. The analysis of the low temperature specific heat gives $\gamma$ = 46 mJ/mol.K${}^2$. The temperature dependence DC magnetic susceptibility $\chi (T)$ confirms the anomaly at 3.3 K and follows the Curie-Weiss law for temperatures above 50~K, with the calculated effective magnetic moment, ${\mu }_{\mathrm{eff}}$ = 3.47(2)~${\mu }_B$/Pr and Weiss temperature ${\theta }_p$ = --7.80(1)~K. This effective magnetic moment value is in good agreement with the Hund${}^{\prime }$s rule theoretical free-ion value of 3.58~${\mu }_B$ for Pr${}^{3+}$. The electrical resistivity data also shows an anomaly at $T_N$ and a broad curvature at intermediate temperatures probably due to crystalline electric field (CEF) effects. The Pr${}^{3+}$ in this structure type has a site symmetry of $C_s$ which predicts a CEF splitting of the $J$ = 4 multiplet into 9 singlets and thus rule out in principle the occurrence of spontaneous magnetic order. In this article we discuss the magnetic order in PrRu${}_2$Ga${}_8$ in line with an induced type of magnetism resulting from the admixture of the lowest CEF level with the first excited state.

6 pages, 4 figures, appeared In the Proceedings of SAIP2017