Microscopic magnetic properties of nonstoichiometric V 2O 3+x—NMR and inelastic spin-flip neutron scattering measurements

Abstract

The local magnetic properties of the V sites in the nonstoichiometric V 2O 3+ x (0 ⩽ x <0.08) have been examined by nuclear magnetic resonance and inelastic spin-flip neutron scattering techniques. The samples with x = 0.01 and 0.02 show a paramagnetic metal (PM)-antiferromagnetic insulator (AFI) transition. In the AFI phase, two distinct 51V NMR signals with hyperfine fields H n = 184.9±0.5 kOe and 71±1 kOe were observed at 1.8 K, which were assigned as due to V 3+ and V 3+ sites, respectively. On the other hand, the samples with x = 0.04 and 0.06 were metallic down to 1.4K, and showed a paramagnetic (PM)-antiferromagnetic (AFM) transition at about 10 K. In these samples, a 51V NMR signal with H n = 58±2 k0 e and one with 〈 H n 〉 = 9 kOe were observed at 1.8 K, which were assigned as due to V 3+-like sites and the matrix V sites, respectively. These results are entirely consistent with those obtained from the neutron experiment. We propose that in the metallic phase (0.04 ⩽ x < 0.08) the minority V 4+-like sites are magnetically localized in the delocalized V matrix and may be responsible for the antiferromagnetic long range order below 10 K.