The simultaneous action of two actual mechanisms of photoinduced alignment effect (PAE) of axial electronic centers is considered. Namely, these mechanisms are: (i) in-center photoinduced reorientations accompanied by photorecharging of centers and (ii) re-occupations of orientational states due to carrier trapping. PAE on Fe-K(3+)-O-1(2-) centers in KTaO3 is considered as an example. The value of the potential barrier between different center orientations (approximate to 0.34 eV) has been determined by linear dichroism measurements of phonon-induced reorientation rates. Quantitative explanation of PAE temporal dependence is achieved.

The paramagnetic resonance of dilute ions in the bulk paramagnetic host is separated from the host response by means of optically detected magnetic resonance (ODMR) using the magnetic circular dichroism (MCD) of the absorption. This result shows that it is possible in principle to extend by means of the ODMR of the absorption the regime of paramagnetic resonance detection of impurity ions to magnetic hosts, which strongly interact with the microwave field and, hence, make the impurity signals unobservable by means of conventional EPR. The observed ODMR signals are attributed to and ions by correlation with the optical bands of these species. By means of ODMR via the Faraday effect it is shown that this effect is due to transitions between Tb levels. The identification of the observed magnetic resonance structures is confirmed by calculations based on known information on and in diamagnetic hosts. The role of molecular fields is discussed.

The analysis of EPR spectra obtained from iron doped KTaO3 crystals in the as-grown state revealed three dominant iron centers: Fe3+-OI, axial Fe-centers with spinS = 3/2 and rhombic Fe3+. By comparison with data from literature possible assignments for the center withS = 3/2 are discussed. For the rhombic species the temperature dependence of the main parameters of the Spin- Hamiltonian was measured. The result makes it most plausible that only one rhombic iron center exists in KTaO3, in contrast with literature. The understanding of the EPR spectra allows us to assign transitions, observed at very low magnetic fields by optically detected magnetic resonance (ODMR), to this rhombic Fe center. On this basis, the magnetic circular dichroism (MCD) of this defect could be identified using the method of tagged-MCD. This spectrum is compared to the tagged-MCD of Fe3+-O1 and of axial Fe4+ centers, which may be generated metastably by optical charge transfer. Considerably different structures in the MCD spectra of both Fe3+ centers indicate different local surroundings and electronic states.

The electron spin resonance of Fe4+OI in KTaO3 has been observed optically (ODMR) via the magnetic circular dichroism (MCD) of absorption. The charge state Fe3+OI was present simultaneously. Fe4+OI was created metastably at low temperatures by light used to detect the MCD.

Tetragonal calcium manganese germanium garnet (Ca3Mn2Ge3O12) is determined to be optically negative. An analysis of the angular dependence of the transmission for a-cut crystals reveals the presence of dichroism. Absorption is largest for extraordinarily polarized light. Both properties allow to determine and orient the crystallographic axes of Ca3Mn2Ge3O12 samples.

A photorefractive effect in terbium gallium garnet with refractive index changes up to Δn = 5 × 10−8 for elementary volume phase holograms is reported. The light-induced refractive index changes can directly be attributed via Kramers-Kronig relations to the observed photochromic and light-induced, linear dichroitic behavior. This can also explain the possibility of writing holograms with orthogonally polarized beams.

Abstract Measurements of the optical absorption, the low frequency electrical conductivity and electron spin resonance of reduced LiNbO3, doped with 6 mol% MgO or 7.25 mol% ZnO in the melts, can consistently be interpreted by assuming that free small polarons are present at room temperature, having a polaron stabilization energy EP = 0.5 eV. At 6K the polarons are slightly bound bv ∼ 0.1 eV. caused by unknown defects.

Two new axial Fe3+ centres. arising after reduction of stoichiometric lithium niobate crystals grown from melts containing K2O, were discovered and investigated by EPR. Their b20 crystal field parameters are equal to 495 and 688 (*10-4 cm-1) and are thus much smaller than b20 for the axial FeLi3+ centre, 1660*10-4 cm-1, which had been studied before. The models of Fe3+ centres in lithium niobate and lithium tantalate crystals are compared and the possible structures-FeNb3+ and FeNb3+-KLi-of the new centres are discussed.