Nuclear Magnetic Resonance in Palladium-Silver Alloys

Abstract

The 109Ag NMR has been studied in a series of Pd1−xAgx alloys by spin-echo techniques in external fields near 55 kOe and at temperatures of 1°–4°K. Knight shifts (K), spin-lattice (T1), and spin-spin (T2) relaxation times were determined for 12 compositions in the range 0.025≤x≤1. The shifts are negative for x≤0.35. From the observed lineshape in the x = 0.025 alloy (K = −1.41%) it is estimated that K = −1.46% in the limit of infinite dilution. After adjustment for an estimated direct contact shift of +0.34%, this value yields a hyperfine field of −140(±10) kOe/μB of palladium d-spin magnetization, which presumably arises from spin polarization of the s conduction electrons by the palladium host. This process is found to be ineffective as a spin-lattice relaxation mechanism. The observed relaxation times T1T increase gradually from a value of 9.6(±0.5) sec·°K for pure silver to a broad maximum of 26(±3) sec·°K near x = 0.3 and remain nearly constant at lower concentrations [T1T = 22(±4) sec·°K for x = 0.025]. The variation of (T1T)−1/2 with composition is qualitatively consistent with the expected variation of the s electron density of states at the Fermi level. The 105Pd spin-lattice relaxation times in palladium metal have been remeasured with the result T1T = 0.7(±0.2) sec·°K.