NMR Study of Microscopic Magnetic Properties of V₆O₁₃

Abstract

Using a single crystal of a substance showing the metal-insulator transition, V₆O₁₃, the microscopic magnetic properties in the metallic, insulating and antiferromagnetic states have been investigated by means of the pulsed NMR technique. In the metallic state the Knight shift and the nuclear-spin lattice relaxation time T₁ were measured in order to clarify the properties of spin fluctuations in the narrow d-bands. It was found that T₁ has the temperature dependence as 1⁄T₁=α+βT. The α term is attributed to the d-spin fluctuations, while the β term is due to the Korringa process. At T_t≈150 K, a half of the V⁴⁺ sites takes singlet spin-pairs resulting in the decrease of the magnetic susceptibility. In the antiferromagnetic state, the magnetic structure was determined as such that the antiferromagnetic spin moments are parallel to the b-axis.