Electron spin resonance of transition metal ions in glasses

Dopant (Mn, Fe, Co and Cu) effects on the structure and dielectric dispersion mechanisms in relaxor PLZT ceramics

“…Figure 1(e) provides some illustration of the evolution of Fe 3+ EPR spectra in the composition series PT → PZT → PLZT1/65/35 → PLZT 8/65/35. Similar to RS where the completely 'glass-like' unstructured bands appear at a certain concentration of La (figure 3), the shapes of the g ef 4.3 absorption in PLZT x/65/35 become completely similar to those observed in glasses and disordered structures [71] only at x 8 (figure 1(e)). Thus, the compositional and structural reasons for the g ef 4.3 absorption in relaxor PLZT appear to be similar to the BO 2− 6 deformations mentioned above in the discussion of the 'glass-like' and 'forbidden' bands in RS (structural disorder).…”

“…However, here, regarding the unmodified structure, we concentrate on the g ef 4.3 absorption, since just the latter is related to relaxor behaviour (see section 3.5.1). A number of arguments such as (a) the g ef 4.3 absorption itself together with other features of spectra [46,67], (b) the g ef 4.3 absorption (Mn and Fe) reported for polycrystals [68,69] and (c) the fact that this absorption is, as a rule, observed in Mn, Fe-doped disordered media [70][71][72] suggest that the d 5 configurations (Fe 3+ , Mn 2+ and Co 4+ ) in a strong crystal field of fully rhombic symmetry are responsible for this absorption [68][69][70][71][72][73][78][79][80]. In terms of the spin-Hamiltonian parameters D and E (representing the axial and rhombic deformation, respectively) this means, correspondingly that (1) |D|, |E| hν (practically |D|, |E| > 0.6hν is sufficient [72], where ν is the microwave frequency),…”

Sol-Gel Synthesis and Structure-Property Relations in Zn_xCu_1-xBi₂O₄ (0≤ x ≤0.6) Spinels

“…2 we show the observed representative EPR lineshapes of the samples along with the computer simulated ones at 14 K. The lineshapes are isotropic with very poorly resolved 4-parallel lines and unresolved perpendicular lines characteristics of axially symmetric 63/65 Cu(I=3/2) lineshapes of a Cu 2+ site. Using an axially symmetric spin-Hamiltonian we simulate the linesahpes and the obtained spin-Hamiltonian parameters are shown in Table 2 along with the isotropic gvalues of the linesahpes at 300 and 77 K. From the trends g ║ >g ┴ > g e (g e = 2.0023) [8] we conclude that the paramagnetic site is Cu 2+ (3d 9 ) which is in a octahedral[O 1/2 -CuO 4/2 -O 1/2 ] environment of oxygens having D 4h symmetry with B 1g as the ground state [9]. Using the relations of the spin-Hamiltonian parameters with the molecular orbital coefficients under D 4h symmetry with the value of free ion dipolar term, P as + 0.03 cm -1 as [10], and also using the criterion [11], A ║ negative and A ┴ positive for 63/ 65 Cu nuclei we calculate the extent of in-plane σ-bonding, α 2 , and the Fermi contact term κ.…”

Determination of the Fe3+/$${\varvec{\Sigma}}$$Fe Ratio in Synthetic Lead Silicate Slags Using X-Band CW-EPR

“…Our previous work [29] showed that the composition related shift in α at high Pb content is mainly because of the broadening of the g = 2.0 feature in the EPR spectrum of Fe 3+ . This broadening may be caused by a larger variety in different local environments of Fe 3+ in high Pb containing silicate glasses [33,35], leading to an increased inhomogeneous line broadening. On the other hand, the larger concentration of nuclei with non-zero spin and atoms with large spin-orbit coupling, and the larger density of low energy vibrational modes in glasses with higher Pb content, may all contribute to a reduction of the spin relaxation time [36,37], producing homogeneous line broadening.…”