Muon spin rotation investigation of theS = 1/2 triangularlattice LiNiO2

Abstract

We have investigated S = 1/2 triangular lattice Li0.98Ni1.02O2 by a zero-field (ZF) and longitudinal-field (LF)μSR technique. Themuon signals from Li0.98Ni1.02O2 could be fitted by a stretched exponential function at low temperatures. At about 30 K the powerk of the stretched exponential function becomes aboutk = 2 for the ZF signal, i.e. the relaxation becomes practically a Gaussian. For theLF-μSR signals theexponent k tendsto become 1 above T = 30 K, i.e. the signal becomes exponential. The relaxation rateλ becomes very high attemperature below T = 10 Kfor the ZF data whereas λ corresponding to LF data shows a maximum at K. The LF relaxation rate remains finite(0.4 µs−1) at the lowest temperature ( K) investigated. This indicates that even at very low temperature muon spin becomesdepolarized because muons pick up low energy excitations from the spin dynamics. We geta rough estimate of the magnetic exchange interaction of about 1 meV from the peak in thespin–spin correlation function.