M. Yu. Artyomov

Trigonal and triclinic Fe3+ paramagnetic centers in ferroelectric Pb5Ge3O11

In the EPR spectra of iron-doped lead germanate single crystals, triclinic Fe3+ paramagnetic centers have been found in addition to trigonal centers. Their contribution increases upon annealing in a chlorine-containing atmosphere. The parameters of the spin Hamiltonian of three triclinic centers assigned to Fe3+-Cl− dimeric complexes have been determined. The localization of iron and chlorine ions in Pb5Ge3O11 has been discussed.

Paramagnetic defects in ZnSe crystals doped with iron ions

The electron paramagnetic resonance (EPR) spectra of iron-doped ZnSe single crystals were studied. In addition to cubic Fe3+ and Mn2+ centers and also Fe2+, and Cr2+ centers, monoclinic Fe3+ complexes locally compensated by Cu+ ions were revealed. Some trigonal centers with a spin of 3/2 were also found and studied. The zero-field splittings of monoclinic centers were measured, and the parameters of the monoclinic and trigonal spin Hamiltonians were determined. The nature of trigonal centers was discussed.

Electron paramagnetic resonance of Gd3+ ions in Ca1 − x − yYxGdyF2 + x + y crystals

Electron paramagnetic resonance of Ca1 − x − yYxGdyF2 + x + y single crystals has revealed spectra that are not typical of gadolinium-doped CaF2 crystals. These spectra have a nearly tetragonal symmetry and are most probably caused by Gd3+ ions localized in yttrium clusters. Weak spectra of tetragonal Gd3+ centers, whose parameters are close to those of a cubic gadolinium center caused by an isolated Gd3+ ion, have been also detected. These centers are attributed to isolated Gd3+ ions localized near octahedral rare-earth clusters or their associations.

Bulk and Surface Defects in Nanoporous SiO2 Ceramic

The methods of electron paramagnetic resonance and optically stimulated electron emission have been used to study the conversion of defects in samples of a nanostructured SiO2 ceramic synthesized by the thermal decomposition of polysilazane HxCyNzSi. The ceramic samples additionally underwent a thermal treatment and were exposed to accelerated electrons.

Paramagnetic Complexes in Zinc Selenide Crystals with Iron Admixture

Paramagnetic resonance of ZnSe: Fe single crystals was studied at 120 K. Parameters of the spin Hamiltonian were determined for the monoclinic dimer complex Fe3+–Cu+ and a second discovered Fe3+ center, which appears due to association of the iron ion with a K+ ion in a Zn2+ position or with a zinc vacancy. Effect of illumination of the zinc selenide samples by blue, green and red light on the paramagnetic resonance spectrum was investigated.

Relaxation of the environment of Gd3+ and Eu2+ impurity ions in the Y3Al5O12 garnet

The second-rank spin Hamiltonian parameters of Gd3+ and Eu2+ orthorhombic centers in crystals of the yttrium aluminum garnet Y3Al5O12 have been analyzed within the framework of the superposition model for the zero-field splitting of the ground state. It has been shown that the description of the experimental data in this model is possible only under the assumption of relaxation of the ligand environment of the paramagnetic impurity.

Orthorhombic centers of rare-earth S-ions in lutetium–aluminum garnet crystals

Electron paramagnetic resonance spectra of Eu2+ and Gd3+ centers in Lu3Al5O12 single crystals have been studied and the parameters of their rhombic spin Hamiltonian have been determined.

Paramagnetic resonance of LaGaO3: Mn single crystals grown by floating zone melting

The EPR spectrum of Mn-doped lanthanum gallate single crystals grown by floating zone melting with optical heating has been studied. In contrast to the crystals grown according to the Czochralski method, no manganese is found in these crystals even after high-temperature annealing in air. The spectral characteristics of Fe3+ and Gd3+ centers in crystals prepared by various methods have been compared in the rhombohedral phase, and the fourth-rank nondiagonal parameters of the Fe3+ trigonal centers have been determined, as well.

Study of ferroelectric phase transition in Pb5Ge3O11 by paramagnetic resonance of Gd3+ centres

The temperature dependence of the fine structure of trigonal paramagnetic Gd3+ centres in Pb5Ge3O11 was investigated in a wide temperature range in the vicinity of structural phase transition. The temperature dependence of the squared order parameter has been constructed based on the obtained data. It was shown that for the adequate description of its behaviour, the sixth-power term in polarization must be taken into account in the expansion of the thermodynamic potential. The orientational dependence of anomalous broadening of electron paramagnetic resonance signals in the vicinity of ferroelectric phase transition was studied. By comparison of the observed behaviour with the angular dependences of the line width that are characteristic of various broadening mechanisms, it was inferred that it can be attributed to defect induced statistical dispersion of fine structure triclinic parameters.

Gadolinium ion pairs in Pb5Ge3O11: EPR investigation

It has been found that a symmetric group of weak satellites of the 1/2 ↔ −1/2 signal of the trigonal Gd3+ center in lead germanate observed in a wide temperature range is caused by transitions of paired complexes of gadolinium ions coupled by the magnetic dipole-dipole interaction.