Electron paramagnetic resonance of Fe³⁺in gallium borate: Superposition model analysis

Abstract

A series of high quality FexGa1−xBO3 single crystals with 0 ≤ x ≤ 1 was prepared and studied by electron magnetic resonance in the temperature range from 4 to 290 K. At low x, only the electron paramagnetic resonance (EPR) of diluted Fe3+ ions is present. The EPR spectra for different orientations of the magnetizing field have been computer simulated. With a conventional spin Hamiltonian including the Zeeman and fine‐structure terms, two different sets of best‐fit parameters have been found. This ambiguity has been resolved on the basis of the general spin Hamiltonian with parameters determined from the crystallographic data using the Newman superposition model. A detailed fitting to the experimental EPR spectra assuming statistical distributions of Fe3+ ligand coordinates has revealed the existence of a certain degree of local disorder in FexGa1−xBO3 single crystals.

Fe x Ga1−x BO3 single crystals: synthesis and characterization

“…8, is typical of isolated Fe 3? in oxygen environment in the case where the Zeeman interaction is comparable with the quadrupole fine structure. The spin Hamiltonian parameters have been determined by computer simulating the EPR spectra with laboratory-made code based on a generalized spin Hamiltonian [23]. Besides, no structurally nonequivalent iron sites have been detected, proving the absence of twinning in the crystals.…”

On the Dependence of the Electron Paramagnetic Resonance Line Intensities on the Microwave Field Orientation

“…where O n ±m are extended Stevens operators (in Ref 3? in GaBO 3 has provided close fits to the experimental EPR spectra [6].…”

“…(S ¼ 3 = 2 ) in GaBO 3 [6]. In this case local symmetry of the paramagnetic ions is trigonal, so that Eq.…”

11B MAS NMR study of Ga1−xFexBO3 mixed crystals

“…The simulation parameters obtained for 11 B are consistent with threefold-coordination and C 3 intrinsic symmetry for the 11 B nuclei. The behavior of the MAS NMR spectra with the increase in iron contents has been related to variations of quadrupole parameters and chemical shift caused by disorder in the local environment This assumption is corroborated with accurate computer simulations of Fe 3 þ EPR spectra [21], showing the existence of a certain degree of local disorder in iron-doped gallium borate crystals. …”

“…Experimental MAS NMR spectra have been computer simulated using a laboratory-developed code explicitly taking into account the distribution of the quadrupole parameters in the most general form, the so-called Maurer's distribution [20]. The results of our EPR study of these crystals have been published elsewhere [21].…”