Li-7 nuclear magnetic resonance spectra and relaxation in Ni1-xLixO

Li-7 nuclear magnetic resonance (NMR) spectra and relaxation rates in Ni1-xLixO, for 0.01 less than or equal to x less than or equal to 0.46 and for 20 less than or equal to T less than or equal to 550 K are presented. For x less than or equal to 0.2 the antiferromagnetic (AF) phase typical of NiO is still observed. The Neel temperatures T-N(x), the temperature dependence of the field at the Li site, and the role of the extra holes in driving the correlated spin dynamics of Ni2+ are derived. In particular, from Li-7 relaxation rates W the hopping frequencies of the holes on the AF background and the energy gaps between itinerant and localized states are extracted. In the mixed regime (x greater than or equal to 0.3, LiNiO2 structure-type) in which partial ordering on alternate Li+ and Ni3+ layers occurs, Li-7 NMR data display the features typical of disordered paramagnets, consistent with a picture of random distribution of Ni3+ (S=1/2), Ni2+ (S=1) and of spin vacancies Li+ (S=0). In particular, for x=0.46, on cooling, paramagnetic-like divergence of the width and of the shift of the NMR line is observed while Li-7 W's indicate slowing down of the spin fluctuations. The fluctuation frequency decreases in the MHz range below a freezing temperature T-f similar or equal to 40 K. (C) 1996 American Institute of Physics.