NMR spin-lattice relaxation rate of heavy fermion superconductor UBe13

Abstract

9Be NMR measurements have been carried out for a single crystal UBe13 with Tc =0.85 K, in order to clarify unusual properties in the normal state. For the applied field parallel to [111] direction, the quadrupole split Be(II) lines gather around the central line. 9Be nuclear spin-lattice relaxation rate was measured for Be(II) sites for H||[111] at 0.85, 7, 15 T. 1/T1 does not depend on applied fields above T*NMR ≈ 5 − 9 K and weakly depends on temperature. 1/T1 at 0.85 and 7 T is proportional to Tn with n = 0.5 − 0.6 down to T = 2 K, suggesting that antiferromagnetic spin fluctuations exist. On the other hand, 1/T1 is suppressed by applied magnetic field. The present field dependence of 1/T1 at low temperatures would give important information about the formation of the heavy quasiparticles in UBe13.