Yb-171 NMR in the Kondo semiconductor YbB12

The Yb-171 nuclear magnetic resonance (NMR) is observed below 10 K in the s ingle crystal of the Kondo semiconductor YbB(12)with the large shift of 66% . The hyperfine coupling constant of 115 T/mu(B) agrees with the calculated value for the J = 7/2 state of free Yb3+ ions, indicating that the the mag netic susceptibility Lit the low-temperature (T) limit is the Van Vleck con tribution within the J = 7/2 multiplet. The nuclear spin-lattice relaxation rate at the Yb sites shows an activated temperature dependence below 15 K with the activation energy of 87 K, which however is completely different f rom the behavior at the B sites. (C) 2000 Elsevier Science B.V. All rights reserved.