Low-Temperature Pressure-Dependence Studies of Knight Shifts and Nuclear Spin-Lattice Relaxation Rates in Cesium and Rubidium Metals

Measurements of the Knight shift K and nuclear spin-lattice relaxation-time T₁ have been carried out on ¹³³Cs and ⁸⁷Rb as a function of hydrostatic pressure to 50 000 psi at 4^∘{}K. For ¹³³Cs, atmospheric-pressure data were also obtained at 27 and 76^∘{}K. The cesium Knight shift and relaxation rate are enhanced by about 18 and 24%, respectively, at the maximum pressure. This corresponds to a 13% increase in the Korringa product K²T₁T, which is attributed to an increase in the exchange enhancement of the spin susceptibility resulting from a strong volume dependence of the band effective mass. The experimental volume and temperature derivatives of K in cesium metal yield an explicit temperature dependence at 4^∘{}K given by ${({{∂}lnK}{{∂}T})}V={-}(0.8±{}0.1)×{}{10}^{{-}4}^∘{}K^-1.