Spin-Glass Ground State in a Triangular-Lattice Compound YbZnGaO 4

We report on comprehensive results identifying the ground state of a triangular-lattice structuredYbZnGaO4 as a spin glass, including no long-range magnetic order, prominent broad excitation continua,and the absence of magnetic thermal conductivity. More crucially, from the ultralow-temperature acsusceptibility measurements, we unambiguously observe frequency-dependent peaks around 0.1 K,indicating the spin-glass ground state. We suggest this conclusion holds also for its sister compoundYbMgGaO4, which is confirmed by the observation of spin freezing at low temperatures. We considerdisorder and frustration to be the main driving force for the spin-glass phase