Nuclear Spin Relaxation of Powdered Metallic Antimony in Liquid 3He

Nuclear spin relaxation studies have been carried out to determine the surface relaxation of powdered Sb immersed in liquid³He. The surface relaxation mechanism was observed to be significantly more effective than the bulk Korringa relaxation rate for temperatures T < 75 mK. This surface relaxation is attributed to the modulation of the dipole-dipole interaction between the Sb spins at the metal surface and the³He spins in the solid-like layer on the surface by the quantum zero-point motion of these³He atoms. The total relaxation has been analyzed in terms of the surface relaxation and the spin diffusion through the bulk of the Sb particles. The experimental results are in excellent agreement with the theory developed for this system. Replacement of the³He by⁴He removes the surface relaxation component and restores the relaxation rates to the bulk value.