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Properties of two lowest electron levels of the Fe2+ impurity ion in a natural amethyst are studied by continuous wave electron paramagnetic resonance spectroscopy in the Q-band. It is established that the these levels present quasi-doublet ± 2 with zero-field splitting of 30.9 ± 0.2 GHz. Orientation of principal magnetic axes and value of g-factor of this paramagnetic center are determined. [ABSTRACT FROM AUTHOR]

Fine structure of ground electron state of Fe4+ impurity ion in a natural amethyst crystal was studied by broadband electron paramagnetic resonance spectroscopy in the frequency range of 34–500 GHz. It is established that energy levels scheme consists of ground quasi-doublet Sz = ± 2, quasi-doublet S z= ± 1 and singlet Sz=0 with zero-field energies ± 4.9 GHz, 435.2 ± 45.4 GHz and 584 GHz, respectively. Parameters of effective spin Hamiltonian describing dependences of electron spin levels on magnetic field are determined. [ABSTRACT FROM AUTHOR]

The temperature dependencies of the spin–lattice relaxation time and the phase relaxation time of 53Cr3+ ion in the Y228SiO5 single crystal are measured at the anti-crossing point via pulsed electron paramagnetic resonance technique at X-band frequencies and in the temperature range from 5 to 80 K. It is found that the phase relaxation time does not change rapidly near the anti-crossing point, whereas in optical experiments with rare-earth ions, the phase relaxation time decreases significantly with a slight deviation of the magnetic field from the anti-crossing point. The effect of spin dynamical decoupling on the phase relaxation time is measured using the Carr–Purcell–Meiboom–Gill (CPMG) multi-pulse sequence. [ABSTRACT FROM AUTHOR]

Monoisotopic 53 Cr 3 + impurity ions in scandium orthosilicate single crystal ( Sc 2 SiO 5 ) are studied by the method of electron paramagnetic resonance in the X-band frequencies. The directions of the main principal magnetic axes and the parameters of the effective spin Hamiltonian that describe the magnetic characteristics of the impurity centers of chromium, which replaces scandium in two structurally nonequivalent positions, are determined. It is shown that the orientation dependencies of the EPR spectra are well described by the second-order spin Hamiltonian corresponding to the orthorhombic symmetry of the local crystal field acting on the impurity ion. It was assumed that the g-tensor and the A-tensor determining the Zeeman energy of electronic levels in a magnetic field and the hyperfine interaction of electron and nuclear spins are isotropic, and the entire anisotropy of the EPR spectra is due to the anisotropy of the D-tensor, which describes the fine structure of electronic levels in a crystalline electric field. A strong dependence of the probability of "forbidden" transitions between hyperfine sublevels of electronic levels on the orientation of an external magnetic field is established. Moreover, for some orientations, the probability of "forbidden" transitions exceeds the probability of "allowed" transitions. [ABSTRACT FROM AUTHOR]

The local environment of neodymium ions in a Y2SiO5 crystal is investigated. The distances between the unpaired electron on Nd3+ and the magnetic nuclei of nearby Y3+ ions are determined from the hyperfine interaction (HFI) parameters obtained from electron spin echo envelope modulation datasets. Available X-ray diffraction data from pure crystals allowed the calculation of distances between different ions thus providing estimations of HFI parameters for Nd-doped single crystals. The simultaneous comparison of HFI parameters and radius-vectors allows the local environment to be derived, and the degree of the distortion generated by impurity ions to be estimated. It is shown that the distances between the neighboring yttrium sites of the unaltered and doped crystals are consistent within 5% accuracy. [ABSTRACT FROM AUTHOR]

The ScSiO single crystals doped with 0.001 at.% of the Nd ion were studied by continuous-wave and pulse electron paramagnetic resonance methods. The g-tensors and hyperfine structure tensors for two magnetically non-equivalent Nd ions were obtained. The spin-spin and spin-lattice relaxation times were measured at 9.82 GHz in the temperature range from 4 to 10 K. It was established that three relaxation processes contribute to the spin-lattice relaxation processes. There are one-phonon spin-phonon interaction, two-phonon Raman interaction and two-phonon Orbach-Aminov relaxation processes. It was established that spin-spin relaxation time is of the same magnitude for neodymium ion doped in ScSiO and in YSiO. [ABSTRACT FROM AUTHOR]

Paramagnetic centers formed by impurity Tm3+ ions in synthetic forsterite Mg2SiO4 were studied by high-frequency tunable electron paramagnetic resonance spectroscopy in the frequency range of 150–315 GHz. Crystals were grown from the melt by the Czochralski technique in slightly oxidizing atmosphere. Several centers distinguished by different zero-field splitting between the ground and first excited singlets were found and investigated. Parameters of the effective spin Hamiltonian for these centers describing the dependence of electron-nuclear sublevels on magnetic field were determined. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) of Ho3+ single ions and Ho3+−Mg2+-vacancy-Ho3+ associates in holmium-doped forsterite single crystals are studied at 9.4, 37.3 and 65–250 GHz. Crystals were grown from melt by the Czochralski technique in slightly oxidizing atmosphere. For both centers, directions of the principal magnetic axes and parameters of the effective spin Hamiltonians describing dependences of electron-nuclear levels on applied magnetic field are obtained. For Ho3+ substituting Mg2+ in the M2 site as the single ion and for Ho3+ ions in dimer centers, values of crystal field parameters related to a real crystal lattice structure are estimated in the framework of the exchange charge model. The calculated crystal field energies, values of the g-factors of the ground Ho3+ quasi-doublet and the directions of the corresponding magnetic moments agree satisfactorily with the data obtained from measurements of EPR and optical absorption and site-selective luminescence spectra. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance spectra of isolated and dimer impurity centers of trivalent chromium ions in the octahedral Ml sites in synthetic forsterite are studied in the frequency range of 65–90 GHz. The measurements are performed at 4.2 K in magnetic field from −0.04 to 0.3 T. The zero-field splitting between spin doublets of the isolated Cr3+ ion Δs = 66.7 GHz and between spin sublevels of the Cr3+-Cr3+ dimer Δd1 = 71.5 GHz and Δd2 = 73.0 GHz is measured directly at zero field. The analysis of the spin Hamiltonian parameters shows that the dimer center consists of a pair of Cr3+ ions with an Mg2+ vacancy between them replacing three Mg2+ ions situated in a quasi-one-dimensional chain aligned parallel to the crystal c-axis. It is found that the exchange interaction in the dimer is ferromagnetic with parameters Jz = 0.47 GHz and Jt = 0.79 GHz. [ABSTRACT FROM AUTHOR]

Two aqueous solutions of oxonitrocomplexes comprising di- and tetravalent platinum atoms, K[(NO)Pt(μ-O)Pt(NO)]· 3HO and K[(NO)Pt(μ-O)Pt (μ-O)Pt(NO)] · 7HO, have been studied byPt andN NMR technique. Both compounds, enriched with theN (95%) isotope, were synthesized by thermal denitrozylation of K[Pt(NO)]. Constants of spin-spin scalar coupling,Pt-N andPt-Pt, were obtained for tetra-and heptameric complexes in aqueous solutions through multiplet simulation. ThePt andN NMR spectra of the same solutions obtained two months after their preparation show signals from the hydrolytic forms of the tetrameric complex as well as the signals from mono- di- and trimeric oxonitrocomplex forms of divalent platinum. All signals of species formed as a result of hydrolysis were identified. [ABSTRACT FROM AUTHOR]