<b>⁵¹</b>V NMR Study of Spin Gap in CaV<b>₄</b>O<b>₉</b>

Abstract

The NMR shift and the nuclear spin-lattice relaxation rate (1/ T 1 ) were measured at the V sites in the two-dimensional compound CaV 4 O 9 . The NMR shift becomes a positive constant below ∼15 K, indicating that the intrinsic spin susceptibility vanishes at low temperatures. The activated T dependence of 1/ T 1 has revealed the dynamical spin gap Δ R ∼104 K, which is rather smaller than the static spin gap determined from the susceptibility Δ S ∼135 K.