OBSERVATION OF A NUCLEAR-MAGNON CONTRIBUTION TO THE NUCLEAR-SPIN-LATTICE RELAXATION OF PT-191 IN FERROMAGNETIC COBALT

We report the first indication For a nuclear spin-lattice relaxation m echanism originating from the coupling of the impurity nuclei to nucle ar magnons. The magnetic hyperfine interaction and the nuclear spin-la ttice relaxation of Pt-191 (T-1/2 = 2.8 d) in fee Co were measured wit h NMR on oriented nuclei at temperatures between 8 and 14 mK in extern al magnetic fields B-ext = 0.1-10 kG. Between B-ext = 5 and 1 kG the r elaxation rate increases bu 2 orders of magnitude. This increase is at tributed to the interaction of Pt-191 with nuclear magnons originating from the Co-59 nuclear spin system.