SPIN DYNAMICS IN CHARGE DOPED ANTIFERROMAGNETS - A LI-7 NMR-STUDY IN NI1-XLIXO

The effects of heterovalent substitutions causing itinerant holes in s trongly correlated 3d electron systems are studied by means of Li-7 NM R in lithium-doped antiferromagnetic NiO. The spin-lattice relaxation rates, driven by the fluctuation of Ni2+ (S = 1) ions, in the temperat ure range 10 K < T < 700 K and in external magnetic fields varying fro m 1T up to 9.4T, are used to obtain insights on the hole hopping and o n their localization. The gaps between itinerant and localized states and their dependence on the doping are thus derived. Furthermore, belo w the charge localization temperature, the slowing-down of the spin ex citations related to the freezing of effective anomalous magnetic mome nts induced on the antiferromagnetic matrix are investigated. A compar ison with the corresponding situation in charge doped La2CuO4 is brief ly addressed.