Motional narrowing in the electron-spin-resonance-spectrum of pentavalent vanadium-compounds

Abstract

The activation energy of the hopping frequency of the vanadium-3dl-electron is derived from the temperature dependence of the ESR linewidth in the following semiconducting, pentavalent vanadium-compounds: NaxV20 s, LixV205 (x<0.02), V20 s weakly doped with WO 3 or MoO 3 (Ea~0.07 eV). In V2MoOs, vanadium-3d 1-electrons are responsible for the electronic conductivity, too.

d 1 Electrons in amorphous semiconducting V2O5 and MoO3 compounds. (ESR measurements)

“…In the ESR spectra of the polycrystalline compound (81 mol-% VzOs) we distinguish only between two ESR lines at g=1.915 and g = 1.985. These are the signals of doped V20 5 crystals, described in [9], narrowed at room temperature by the hopping process of the 3d 1 electron. In the 3 cm band we observe one ESR line with a distorted shape.…”

“…The d a electrons are mobile [3,4]. However, up to room temperature the hopping frequency of the vanadium 3d ~-electrons remains below 200 MHz, contrary to the crystalline V205 where the larger hopping frequency leads to motionally narrowed ESR lines [9].…”

Sol–gel synthesis and characterization of xCuO–(1 − x)Bi 2 O 3 (0.15 ≤ x ≤ 0.55) glasses by magnetic and spectral studies

“…Thus, the derivative peak-to-peak width, Δυ, is a measure of activation energy of hopping, E a , of the small polaron in the glassy matrices. Using the relation [8] of activation energy of hopping involving the derivative EPR peak-to-peak linewidth, Δυ, we calculate the values of activation energy, E a , of the glasses, and show these in Table 3. The extremely low values of the activation energies of the glasses~1 × 10 − 4 eV is of the order of lattice vibrational modes (~10 11 Hz).…”

“…These properties arise from the thermally assisted hopping of Cu 2+ (3d 9 ) electron, which is essentially a 'small polaron' [7], from a lower valent Cu + (3d 10 ) site to a higher valent Cu 2+ (3d 9 ) site. It is reported in literature that the thermally assisted hopping rate of small polaron has marked effect on the electron paramagnetic resonance (EPR) lineshapes [8]; and even at a very low temperature, the thermal hopping rate of small polaron is fast enough to smear out the electron spin-nuclear spin hyperfine interaction to give rise to motionally narrowed EPR lineshapes [9]. In such a situation, it is known that the temperature dependent derivative EPR peak-topeak linewidth of the glass is a measure of the activation energy of hopping [8], E a , of the small polaron.…”

Charge Compensation of Fe3+ Ions in V2 O5 (ESR Measurements)

“…I n addition to the two Fe3+ spectra all V,O, crystals show the ESR signal of the mobile vanadium 3dl electron with a g-value s 2 [3]. Relative intensity measurements were performed in the 8 mm band for H, 11 a.…”