Nuclear Spin Relaxation in Transition Metals; Core Polarization

The nuclear relaxation induced by core polarization (c.p.) in a transition metal is calculated in the tight-binding limit. It is shown that a Korringa-like relation exists between the c.p. Knight shift and the c.p. relaxation rate, but with a factor that inhibits relaxation, the numerical value of which depends on the relative weight of ${\Gamma }_5$ and ${\Gamma }_3$ orbitals at the Fermi surface. Using estimates of the hyperfine fields, the relaxation rates associated with the contact, c.p., and orbital interactions are calculated for three transition metals. It is found that all three processes make significant contributions. The agreement with the measured relaxation rates is satisfactory considering the uncertainties in the estimated numbers.