B-11 NMR study of TbB4

Abstract

We have performed B-11 nuclear magnetic resonance (NMR) measurements on a single crystal of TbB4 to investigate local electronic structure and 4f spin dynamics. B-11 NMR spectrum, Knight shift, spin-lattice and spin-spin relaxation rates, 1/T-1 and 1/T-2, were measured down to 5 K at 8 T. B-11 NMR shift and linewidth are huge and strongly temperature-dependent due to the 4f moments. In addition, both are proportional to magnetic susceptibility, indicating that the hyperfine field at the boron site originates from the 4f spins of Tb. Below T-N, the single broad resonance peak of B-11 NMR splits into several peaks reflecting the local magnetic fields due to antiferromagnetic spin arrangements. The spin-lattice relaxation rate, independent of temperature above T-N, decreases significantly below T-N confirming huge suppression of spin dynamics. (c) 2006 Elsevier B.V. All rights reserved.