Low-temperature properties of theS=12spin systemYb3Ru4Al12with a distorted kagome lattice structure

Abstract

We have synthesized single crystals of ternary intermetallic ${\mathrm{Yb}}_{3}{\mathrm{Ru}}_{4}{\mathrm{Al}}_{12}$ with a distorted kagome lattice structure, and investigated the low-temperature resistivity, specific heat, magnetization, and magnetic phase transitions. ${\mathrm{Yb}}_{3}{\mathrm{Ru}}_{4}{\mathrm{Al}}_{12}$ is the first $4f$ system that has a ${\mathrm{Gd}}_{3}{\mathrm{Ru}}_{4}{\mathrm{Al}}_{12}$-type crystal structure where antiferromagnetic interaction acts on the spin. The crystal electric field (CEF) ground state of this compound is determined as a well isolated twofold degenerate state that is subjected to a strong easy-plane-type magnetic anisotropy. In the present study, the spin system of ${\mathrm{Yb}}_{3}{\mathrm{Ru}}_{4}{\mathrm{Al}}_{12}$ is regarded as an AFM $XY$ model of $S=1/2$. This compound undergoes successive magnetic phase transitions at 1.5 and 1.6 K, and the resistivity exhibits ${T}^{2}$ behavior below 1 K. The ratio of the coefficient of the ${T}^{2}$ term in the resistivity $A$, and that of the electronic specific heat coefficient ${\ensuremath{\gamma}}_{0}$, deviates from the Kadowaki-Woods (KW) law. The successive phase transitions and low-temperature properties of ${\mathrm{Yb}}_{3}{\mathrm{Ru}}_{4}{\mathrm{Al}}_{12}$ where geometrical frustration and heavy fermion behavior occur are discussed.