Microscopic Magnetic Properties of V₃O₇

Abstract

Nuclear Magnetic Resonance of ⁵¹V has been investigated in both the antiferromagnetic and the paramagnetic states of V₃O₇. Two signals associated with magnetic V⁴⁺(3d¹) sites have hyperfine fields (H_N) of −199.8 and −208.7(±0.3) kOe at 1.25 K which are dominated by intra-ionic dipolar field. The temperature dependence of H_N was well described by an equation H_N=H_NO(1−AT²) with A=(16.0±0.5)×10⁻³ (K⁻²) in the range 1.32≤T≤2.22 (K). Three signals from V⁵⁺ sites were also observed. Magnetic susceptibility at high and low field behaves differently below the Néel temperature of 5 K. These results together with the convex curve of magnetization versus field in the paramagnetic state are discussed in terms of the insulating low-dimensional magnetic system with small anisotropy energy and predominant ferromagnetic interaction along linear chains.