Electron spin resonance of Gd3+ in glasses of the soda-silica-yttria system

Abstract

The electron spin resonance of the Gd3+ ion has been studied in two series of glasses having the molar compositions 6SiO2:5Na2O: x (Gd2O3 + Y2O3) with 0 ≤ x ≤ 0.5 and 500SiO2: x Na2O:1Gd2O3 with 2.5 ≤ x ≤ 494. The spectra were nearly independent of temperature and sample composition, but varied strongly with microwave frequency in the range 5.4–38.4 GHz. The data were interpreted in terms of the spin Hamiltonian for a strong cubic crystal field and also in terms of the usual rhombic spin Hamiltonian H = g 0β H · S + D[Sz2 − (1/3)S (S + 1)] + E(Sx2 − Sy2) with S = (7/2). Computer calculations were made yielding all possible effective g values for this latter Hamiltonian for all physically distinct combinations of the crystal field parameters when the Zeeman field H was restricted to the x, y, or z direction. The resonance features were related to three distinct sites for the Gd3+ ion. The spectra are indicative of a chemically heterogeneous glass matrix composed of soda-rich, silica-rich, and diffuse transition regions. The heterogeneities were found to exist over the entire range of compositions studied. Variations in the resonance intensity associated with the soda-rich region suggest the existence of a very well-defined substructure within the region. The data indicate that the substructure is related to the fundamental structural features of the possible crystalline compounds which can exist within the composition range.

EPR Study of Gadolinium(III) Complexes with Heteropolyanions: [Gd(SiW11O39)2]13-and [GdP5W30O110]12-

“…The g-values < 2.0 are almost similar, and only the small di fferences are observed for g > 2.0. On the basis of this similarity and taking into account the spin-Hamiltonian calculations by Nicklin et al [12] (like in our previous papers [2,3]), it is possible to suppose the existence of the Gd3+ ion in two different surroundings: in a strong crystal field of rhombic symmetry and in a weak crystal fueld.…”

“…Detailed analysis of the U-spectrum was also performed b y Nicklin et al [12]. They attributed these three features to the following kinds of crystal fields: weak cubic or a rhombic site (g = 2.0), intermediate crystal field (g = 2.8) and strong cubic field (g = 6.0).…”

Quantitative EPR of an S= 7/2 system in thionine‐oxidized MoFe proteins of nitrogenase

“…Fig. 7 presents a wide scan at an intermediate temperature of 36 K appropriate for the detection of EPR from the highest two doublets. The range directly around g = 2 is disturbed by a radical signal produced by the added thionine.…”

“…The above is called an exact calculation of g values. Nicklin et al have proposed an approximate calculation using perturbation theory [36]. They noted that the 8 x 8 matrix in zero field (ix.…”

The Interpretation of Broadened Gd3+ EPR Spectra of Polycrystalline Ceramics

“…Recently Cugunov and Kliava [7] have attributed this powder spectrum to a superposition of a spectrum due to a rather well defined site of the Gd3+ ions with rhombic or lower symmetry (geff x 6) and a broad Gaussian line arising from clusters of Gd3+ ions (geff = 2 ) . However, they did not explain, why there would be two totally different paramagnetic sites and why the line a t g,ff = 6 disappears as the frequency is increased [6]. Although it might be possible that the Gd3+ ions can form their own environment in glasses, this is not very likely in the PLZT materials, where the overall structure is well defined.…”