139La NMR Studies in LaIn3

Abstract

Normal‐state nuclear magnetic resonance studies of the superconductor LaIn₃ have been made in order to investigate the origin of the large temperature‐dependent normal‐state susceptibility χ attributed to exchange enhancement of the La d‐electron spin susceptibility. The ¹³⁹La Knight shifts, linewidth, and nuclear‐spin relaxation times (T₁ and T₂) have been measured with cw and pulsed techniques from 1.6°K to 300°K. The Knight shifts (+0.402%±0.002% at 1.6°K−+0.371%±0.002% at 300°K) vary linearly with χ. The relaxation times vary from T₁T = 1.1±0.05 sec °K at 4.2°K to T₁T = 1.6±0.1 sec °K at 300°K. The small magnitude and temperature dependence of the La T₁ and Knight shift as well as the value of the Korringa product K²T₁T/S of 1.28 at 4.2°K appears in the independent band approximation to be inconsistent with the expected large La d‐band hyperfine contribution. This suggests a breakdown of the independent band approximation in LaIn₃ due to interference effects between the various hyperfine interactions.