A study of high-quality SrTiO3 single crystals doped with the Mn4+ ions in the cubic phase (T > 105 K) with X-band electron paramagnetic resonance reveals direct correspondence between a shape of a sample and magnetic anisotropy of the impurity Mn4+ centers. In particular, for a sample with the shape of a square base rectangular prism, a size of (a × a × h) and faces perpendicular to the <100> crystallographic directions, zero-field splitting parameter D is approximately proportional to (a / h − 1) quantity. Temperature dependence of D indicates that this peculiar symmetry lowering is a feature characteristic for the cubic Fm3m phase of the strontium titanate. Diminishing of the D value with the decrease of the surface roughness for a thin (001)-oriented SrTiO3:Mn platelet shows that the observed effect originates from the sample surface.
Phosphate glasses of mol% xAl2O3:(40-x)Ag2O:60P2O5 have been prepared and studied by different techniques. X-ray diffraction measurement (XRD) has indicated the amorphous nature of the glasses. The hardness of the glasses increases with increasing Al2O3 concentrations. Data based on 27Al, 31P MAS NMR and Fourier transform infrared (FTIR) spectroscopy has been presented. The structural changes within the ternary phosphate glasses were correlated with that of the simple binary silver phosphate glasses. The obtained data led to suggest that aluminum plays a dual role, i.e., acts primarily as intermediate ions which means that Al2O3 enters the network of the glass both as a modifier and glass former. But silver oxide acts as a strong glass modifier. The number of non-bridging oxygen bonds (NBO) on average in the phosphate network decreases with increasing Al content. The Al2O3 in the structure of glasses exists in both Al(6) and Al(4). The concentration of Al(6) increases with increasing Al2O3 content. The concentration of Al(4) is much lower than that of Al(6) in the glass of 20 mol % Al2O3.
The studies of chemical processes in spatially confined conditions are of interest from the fundamental and industrial points of view. By means of the W-band EPR and 1H Mims electron nuclear double resonance (ENDOR) we show that the radiation-induced paramagnetic centers (E') in the synthetic nanoporous silica opals could be used as sensitive probes to investigate the surface modification and, potentially, reactions of polymerization in the confined by opal pores.
In the paper, we report on growth conditions, structure characterization, magnetic and magnetoresonance studies of thin-film Fe/Ag/Co/CoO heterostructure deposited ontop of the single-crystal (001)-MgO substrate utilizing in situ combination of molecular beam epitaxy and magnetron sputtering. The molecular beam deposition was applied to grow the first, iron layer epitaxially on MgO realizing the 45-degree lattice matching between the magnesium oxide and the body-centered cubic iron. Subsequent silver layer was also grown epitaxially with the favorable 45-degree lattice matching between the iron and silver. Next, Co-metal and the top, cobalt oxide, layers were deposited by magnetron sputtering and reactive sputtering, respectively, after moving the sample into a magnetron sputtering chamber without breaking the ultra-high vacuum conditions. Magnetometry and ferromagnetic resonance studies of the resulting heterostructure have revealed a combination of the four-fold and uniaxial anisotropies in the film plane at temperatures well above the Neel temperature for antiferromagnetic CoO (TN = 291 K). After field-cooling of the sample down to T = 180 K, ferromagnetic resonance measurements following the major magnetic hysteresis loop have shown a correlated precession of the iron and cobalt layers magnetizations giving the evidence of the interlayer coupling through the silver interlayer.
A review of the twenty-year history of the activities of the International School of Young Scientists "Actual problems of magnetic resonance and its applications" in Kazan, Russia, is presented.
The home-built pulse NMR spectrometer for 3He investigations is described in this article. It operates in the 1.5-4.2 K temperature range, 0-850 mT magnetic field range, and 3-150 MHz frequency range with a dead time as short as 8 μs at 8 MHz that makes possible multinuclear NMR measurements. The spectrometer includes: saturation-recovery and inversion-recovery pulse sequences for spin-lattice relaxation time measurements by FID and Hahn echo amplitude measuring, CPMG pulse sequence for spin-spin relaxation time measurements, pulse gradient coils for diffusion measurements and a possibility to modify surface of porous samples by preadsorption of certain amount of nitrogen. The block diagrams of the spectrometer, the transmit-receive path and the amplifier are also presented.
