Magnetic and transport properties of the mixed-valent compoundYbRh2Ga

Abstract

We report the measurements of specific heat, electrical resistivity, magnetic susceptibility, Hall coefficient and thermoelectric power on a ternary compound of ${\mathrm{YbRh}}_{2}\mathrm{Ga},$ which crystallizes in the triple-hexagonal ${\mathrm{Na}}_{3}\mathrm{As}$-type structure with the space group ${P6}_{3}\mathrm{cm}.$ ${\mathrm{YbRh}}_{2}\mathrm{Ga}$ remains in a paramagnetic state down to 1.2 K. The magnetic susceptibility exhibits a broad maximum around 90 K for $H\ensuremath{\parallel}c$ or 170 K for $H\ensuremath{\perp}c,$ respectively. Such maximum is a characteristic of the Ce- and Yb-based mixed-valent compounds. The temperature dependence of electrical resistivity shows an S-type behavior. The electronic specific heat coefficient is 36.6 ${\mathrm{m}\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{K}}^{2}$, which is nine times larger than that of ${\mathrm{YRh}}_{2}\mathrm{Ga}$ (3.9 ${\mathrm{m}\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{K}}^{2}$) with no $4f$ electron. The thermoelectric power $(\ensuremath{\Delta}T\ensuremath{\parallel}c)$ shows a broad minimum at about 120 K with a relatively large negative value, \ensuremath{\sim}-36 \ensuremath{\mu}V/K, which is typical for Yb-based spin-fluctuation systems. The Hall coefficient $(J\ensuremath{\parallel}c,H\ensuremath{\perp}c)$ exhibits a maximum around 60 K; at higher temperatures it varies with temperature in a manner suggestive of skew scattering. All of the measurement results indicate that ${\mathrm{YbRh}}_{2}\mathrm{Ga}$ is a typical mixed-valent system. The anisot-ropy observed in ${\mathrm{YbRh}}_{2}\mathrm{Ga}$ indicates anisotropic hybridization between localized $4f$-electron and conduction elections.