Fluctuation Effect on the Knight Shift of Superconducting Al Fine Particles

Abstract

The Knight shift of superconducting Al fine particles is measured at temperatures between 0.5 and 4.2 K in magnetic fields of 3.7 and 6.5 kOe. The transition temperature is found to rise with decreasing particle size and is 1.40, 1.43 and 1.54 K for the sample with an average diameter of 170, 130 and 80 Å, respectively. The large fluctuation effects on the Knight shift are observed in such fine particles. The results exhibit good agreement with the fluctuation theory in which the pair breaking of the magnetic field is taken into account. In the sample with an average diameter of 80 Å, the deviation from the fluctuation theory is observed below T_c and is discussed in connection with the discrete nature of one-electron energy levels.