Magnetic resonance study of a vanadium pentoxide gel

Abstract

In this work we report results from continuous-wave (CW) and pulsed electron paramagnetic resonance (EPR) and proton nuclear magnetic resonance (NMR) studies of the vanadium pentoxide xerogel V2O 5:nH2O (n ≈ 1.6). The low temperature CW-EPR spectrum shows hyperfine structure due to coupling of unpaired V4+ electron with the vanadium nucleus. The analysis of the spin Hamiltonian parameters suggests that the V4+ ions are located in tetragonally distorted octahedral sites. The transition temperature from the rigid-lattice low-temperature regime to the high temperature liquid-like regime was determined from the analysis of the temperature dependence of the hyperfine splitting and the V4+ motional correlation time. The Electron Spin Echo Envelope Modulation (ESEEM) data shows the signals resulting from the interaction of 1H nuclei with V4+ ions. The modulation effect was observed only for field values in the center of the EPR absorption spectrum corresponding to the single crystals orientat