⁵¹v NMR Studies of Vanadium “Monoxide” VO_1.25

The microscopic magnetic properties of vanadium “monoxide” VO_1.25 have been investigated by ⁵¹V NMR at temperatures from 1.2 K to 300 K. Two kinds of resonance corresponding to different electronic states were observed. One comes from the nearly nonmagnetic majority sites and it is concluded from the temperature dependences of both the nuclear relaxation rate and the with of the spin-echo spectrum that VO_1.25 orders magnetically below 5 K. At 1.2 K in the ordered state, the other kind of resonance was observed around 200 MHz under zero external field, so the magnetic ordering is ascribed to these small numbers of V³⁺-like sites. Curie-Weiss type temperature dependence of the susceptibility in the paramagnetic state can also be accounted for by presuming that about 8% of V ions are V³⁺, with a localized moment of 2 μB. The crystallographical origin of the V³⁺-like sites is also discussed.