Fast Field Cycling NMR Study of Magnetomechanic Induced Acoustic Waves in Ferrogelatine

E. ANOARDO; F. BONETTO; R. KIMMICH

Leipzig, Alemania

Conferencia; 15º European Experimental NMR Conference (ENCC); 2000

Universidad de Leipzig

In this work we report a study about the influence of an external AC magnetic perturbation in the spin-lattice relaxation time of ferromagnetic doped gelatins (ferrogelatin). Oscillating nano-size ferromagnetic particles were used as local sonic sources in doped gels. For comparison, we studied the same effect in a sample without dopants. Because of the effect we are interested is maximum when the perturbation and Larmor frequencies are coincident, the evolution of the proton magnetization contains information about two processes: the spin-lattice relaxation and spin energy absorption from the perturbing magnetic field. As we were only interested in externally induced dynamical processes (observable through the proton spin-lattice relaxation), we had to discriminate both effects. Fast field cycling NMR experiments combined with sinusoidal magnetic low frequency perturbation were used to study these phenomena. Observable direct effects of the audio field on the spin-system are also discussed. A noticeable shortening of the relaxation time is observed.