NMR study of the superconductor RNi₂B₂C (R = Y, Lu)

Abstract

Measurements of the ¹¹B NMR spectrum and spin-lattice relaxation rate, 1/T₁ in the normal and the superconducting states of a quaternary boro-carbide superconductor RNi₂B₂C (R = Y, Lu) are reported. In the superconducting state, two kinds of ¹¹B NMR spectra have been observed; one ¹¹B signal comes from the superconducting region in the sample and shifts to higher magnetic field due to the demagnetizing field, the other from the normal-metal region with no appreciable shifts. With decreasing temperature, 1/T₁ in the superconducting state decreases rapidly with no appreciable enhancement just below T_c. In the normal state, 1/T₁T increases with decreasing temperature presumably due to antiferromagnetic Ni spin fluctuations. Similar behaviors on B NMR in RNi₂B₂C (R = Y, Lu) were observed in the normal and the superconducting states.