Abstract. We have performed ¹¹B NMR measurements in ¹¹B enriched MgB₂ powder sample in the normal phase. The Knight shift was accurately determined by using the magic angle spinning technique. Results for ¹¹B and ²⁷Al Knight shifts (K) and relaxation rates (1/T₁) are also reported for AlB₂. The data show a dramatic decrease of both K and 1/T₁ for ¹¹B in AlB₂ with respect to MgB₂. We compare experimental results with ab initio calculated NMR relaxation rates and Knight shifts. The experimental values for 1/T₁ and K are in most cases in good agreement with the theoretical results. We show that the decrease of K and 1/T₁ for ¹¹B is consistent with a drastic drop of the density of states at the boron site in AlB₂ with respect to MgB₂.

Print publication: Issue 2 (February 2003)
Received 29 June 2002
Published 30 December 2002