NMR and spin relaxation inLaGa1−xMnxO3:Evidence for thermally activated internal dynamics

N. Noginova, E. Arthur, T. Weaver, G. B. Loutts, V. A. Atsarkin, D. G. Gotovtsev
2004 Physical Review B  
Single crystals of diamagnetically diluted manganites, LaGa 1Ϫx Mn x O 3 (xϭ0 -0.2) have been investigated by means of magnetic-resonance techniques. Detailed study was performed of the NMR line shape, spin-spin and spin-lattice nuclear relaxation of 69 Ga and 71 Ga nuclei. The analysis of the temperature and concentration dependencies of the spin-relaxation rates was supported by additional measurements on 139 La nuclei and electron-spin resonance on Mn electron-spin system. The electrical
more » ... rupole mechanism of nuclear-spin relaxation is shown to be dominant at low Mn concentration (xр0.005), whereas the magnetic dipolar interaction with the Mn electron spins is prevalent at xу0.02. The obtained data suggest the presence of thermally activated internal motion with the activation energy of about 50 meV that governs the Mn 3ϩ electron spinlattice relaxation and, via dipolar interaction, the nuclear-spin relaxation of the host nuclei. In the scenario suggested, this motion can be related to the hindered Jahn-Teller dynamics of the Mn 3ϩ ions linked to clusters or pinning defects.
doi:10.1103/physrevb.69.024406 fatcat:4k24lvbrnzbrpc2fk2qo64s6pu