Structural, magnetic, thermodynamic and electrical transport properties of a new compound $\mbox{Pr}_2\mbox{Rh}_{2}\mbox{Ga}$

Abstract

A new ternary intermetallic compound $\mathrm{P}{\mathrm{r}}_2\mathrm{R}{\mathrm{h}}_2\mathrm{Ga}$ was synthesized by arc-melting and was characterized by powder X-ray diffraction (PXRD), magnetization, heat capacity ${\mathrm{C}}_p(\text{T})$, and electrical resistivity $\rho (T)$ measurements. PXRD patterns revealed that $\mathrm{P}{\mathrm{r}}_2\mathrm{R}{\mathrm{h}}_2\mathrm{Ga}$ crystallizes in the $\mathrm{L}{\mathrm{a}}_2\mathrm{N}{\mathrm{i}}_3$-type of orthorhombic structure with the space group $Cmca$. The temperature variation of magnetic susceptibility, ${\mathrm{C}}_p(\text{T})$ and $\rho (T)$ confirmed that $\mathrm{P}{\mathrm{r}}_2\mathrm{R}{\mathrm{h}}_2\mathrm{Ga}$ exhibits a ferromagnetic behavior with the transition temperature of 18 K. The estimated Sommerfeld coefficient $\gamma$ = 640 mJ/($Pr.mole.{\mathrm{K}}^2$) from the ${\mathrm{C}}_p(\text{T})$ results in the paramagnetic region just above $T_C$~was large in comparison to ordinary metals. In the paramagnetic region $\rho (T)$ data showed a metallic behavior characteristic of electron - phonon scattering. The maximum negative magneto-resistance at high field occurs in the region near the magnetic phase transition temperature. The maximum value of magnetic entropy change ($-\mathrm{\Delta }{\text{S}}_{\mathrm{M}}$) and adiabatic temperature change ($\mathrm{\Delta }{\text{T}}_{\mathrm{ad}}$) are $8.2J/kg.K$ and $3.6\mathrm{K}$, respectively, around the transition temperature for the change of magnetic field 0-9 T. The calculated refrigerant capacity is $70J/kg$, and $135J/kg$ for a change of magnetic field 0-5 T and 0-9 T, respectively. Arrott plot derived from isothermal magnetization and the universal scaling plot by normalizing $-\mathrm{\Delta }{\text{S}}_{\mathrm{M}}$ confirm that the compound undergoes a second order ferromagnetic to paramagnetic phase transition.

9 pages, 13 figures