M. L. Falin

Electron paramagnetic resonance and optical spectroscopy of Yb3+ ions in SrF2 and BaF2; an analysis of distortions of the crystal lattice near Yb3+

SrF2 and BaF2 crystals, doped with the Yb3+ ions, have been investigated by electron paramagnetic resonance and optical spectroscopy. As-grown crystals of SrF2 and BaF2 show the two paramagnetic centres for the cubic (Tc) and trigonal (T4) symmetries of the Yb3+ ions. Empirical diagrams of the energy levels were established and the potentials of the crystal field were determined. Information was obtained on the SrF2 and BaF2 phonon spectra from the electron-vibrational structure of the optical spectra. The crystal field parameters were used to analyse the crystal lattice distortions in the vicinity of the impurity ion and the F− ion compensating for the excess positive charge in T4. Within the frames of a superposition model, it is shown that three F− ions from the nearest surrounding cube, located symmetrically with respect to the C3 axis from the side of the ion-compensator, approach the impurity ion and cling to the axis of the centre when forming T4. The F− ion located on the axis of the centre between the Yb3+ ion and ion-compensator, also approaches close to the impurity ion.

EPR and optical spectroscopy of Yb3+ ions in CaF2: an analysis of the structure of tetragonal centers

CaF2 crystals doped with Yb3+ ions have been studied by electron paramagnetic resonance (EPR) and optical spectroscopy. EPR spectra of paramagnetic centers (PCs) for cubic (Tc) and tetragonal (Ttet) symmetries were identified. Empirical energy level diagrams were established and crystal field parameters were determined. Information on the CaF2∶Yb3+ phonon spectra was obtained from the electron-vibrational structure of the optical spectra. The crystal field parameters were used to analyze the crystal lattice distortions in the vicinity of the Yb3+ ion. Within the framework of a superposition model, it is established that four F− ions located symmetrically with respect to the fourfold axis from the side of the ion-compensator approach the impurity ion and deviate from the PC axis. The second set of four fluorine ions also approaches the Yb3+ ion and the PC axis. The ion-compensator F− also approaches considerably the impurity ion.

Spectrometer for optical detection of magnetic resonance: Magneto-optical study of Yb3+ in BaF2 single crystal

A home-built multifunctional computerized spectrometer for optical detection of magnetic resonance (ODMR) is described. Preliminary results of studying Yb3+ ions in BaF2 single crystal by electron paramagnetic resonance, ODMR and optical spectroscopy are presented.

Transferred hyperfine interaction of a Yb3+ trigonal centre in KMgF3

The investigation of a Yb3+ trigonal centre in KMgF3 was carried out by means of ENDOR. Expressions for the frequencies for ENDOR transitions in trigonally distorted complexes for arbitrary magnetic field orientation with respect to the crystallographic axes were obtained. A structural model of the centre was determined. The parameters of interaction of Yb3+ with F ions of the nearest environment were also determined. A method to determine the absolute signs of the crystal field parameters B43 and B63 was suggested. The microscopic calculation of crystal lattice deformation in KMgF3 near a paramagnetic impurity was carried out. The microscopic analysis of transferred hyperfine interaction parameters for an ion in a non-S state and having a local non-cubic symmetry, taking into account the effects of the spin polarisation of the outer filled 5s and 5p shells of the rare-earth ion, has been carried out for the first time.

EPR and optical spectroscopy of Yb3+ ions in single crystal CsCaF3

CsCaF3 crystals doped with Yb3+ were studied using EPR and optical spectroscopy methods. Several types of paramagnetic centers of Yb3+ were found including a paramagnetic center in an uncommon 12-coordinated position. The schemes of the energy levels of the observed centers are determined and the potentials of the respective crystalline fields are calculated.

The peculiarities of electron-nuclear and pseudo-Zeeman interactions of 19F nuclei in KZnF3:Er3+

The investigation of Er3+ (4f11) ions in a KZnF3 crystal is carried out by means of electron-nuclear double resonance. The parameters of the interaction of Er3+ with F- ions of the nearest environment are determined. The microscopic calculation of these parameters is carried out. Also, the microscopic calculation of the pseudo-Zeeman interaction parameters is carried out for the first time.

EPR and optical spectroscopy of neodymium ions in KMgF3 and KZnF3 crystals

KMgF3 and KZnF3 crystals doped with Nd3+ ions were studied using EPR and optical spectroscopy methods. Several types of paramagnetic centers of Nd3+: KMgF3 — two of tetragonal and one of rhombic symmetry; KZnF3 — one of tetragonal and one of trigonal symmetry were found. Parameters of the corresponding spin Hamiltonians were determined. Using optical spectroscopy paramagnetic centers Nd2+ and Nd4+ in KMgF3 were found.

Antiferromagnetic properties of Cr2V4−xMoxO13 + x2 as detected by EPR

Abstract Electron paramagnetic spectra of Cr 2 V 4−x Mo x O 13 + x 2 were studied between 300 and 4.1 K at X-band. Temperature dependence of the EPR linewidth shows that the substance belongs to a group of one-dimensional antiferromagnets with a Neel temperature T N = 3.6 ± 2 K . Optical absorption bands observed at about 20,000 cm −1 and 13,300 cm −1 are assigned to the transitions 4 A 2g ⇒ 4 T 1g and 4 A 2 g ⇒ 4 T 2 g , respectively. These are correlated with the measured g eff. value. In the vicinity of T N two new EPR lines appear, one of which behaves like a soliton signal arising from moving domain walls in one-dimensional antiferromagnets.