Kira Seleznyova

Modelling the magnetic dipole

Three different models of a magnetic dipole, viz., a uniformly magnetised sphere, a circular current loop and a pair of fictitious magnetic charges, have been systematically analysed within the formalism based on the vector potential of the magnetic field. The expressions of the potentials and magnetic fields produced by each dipole model have been obtained. A computer code has been put forward in order to visualise magnetic field lines for different dipole models. It has been shown that the magnetic field outside the uniformly magnetised sphere coincides with that of a point dipole. The other two models give considerably different results at distances small or intermediate in comparison with the dipole size.

11B MAS NMR study of Ga1−xFexBO3 mixed crystals

Mixed iron-gallium borate crystals Ga1-xFexBO3 have been studied by Magic Angle Spinning (MAS) NMR of (11)B isotope. Experimental MAS NMR spectra have been computer simulated using a laboratory-developed code. The quadrupole parameters and isotropic chemical shift for (11)B are consistent with threefold-coordination of boron atoms. A detailed fitting to the experimental NMR spectra reveals the existence of a certain local disorder in Ga1-xFexBO3 crystals.

Understanding the magnetocrystalline anisotropy of iron borate

Magnetocrystalline anisotropy of iron borate is expected to have two contributions: the crystal field one and the dipole-dipole one. The crystal field contribution is calculated through the perturbation theory using the spin Hamiltonian parameters of isolated Fe3+ ions in diamagnetic gallium borate. The dipole-dipole interaction energy is calculated for two models of extended dipoles having non-negligible size.

Fitting MAS NMR spectra in crystals with local disorder: Czjzek's vs. Maurer's model for 11 B and 71 Ga in polycrystalline gallium borate

A comparative analysis of the Czjzeks and Maurers models of the joint distribution density of NMR quadrupole parameters has been carried out in view of their application to account for spectra broadening induced by local disorder in crystals. As an example of such an application, we have considered Magic Angle Spinning NMR of 11B and 71Ga isotopes in polycrystalline gallium borate. Computer simulations carried out using both models unambiguously show that in the case of low local disorder the Maurers model, in contrast to the Czjzeks model, provides satisfactory fits to experimental NMR spectra.

Synthesis of composite structures on the basis of GaBO3 and FeBO3 trigonal crystals

Film of iron borate FeBO3 is of a great interest as a model object for various scientific studies and is a promising material for practical applications in different branches of experimental science and engineering. Thin magnetic films of FeBO3 on GaBO3 single crystal substrate were prepared by a liquid phase epitaxy route. In order to observe a mechanism of film formation we have carried out optical microscopy studies. X-ray diffraction analysis has confirmed the existence of the FeBO3 layer on the GaBO3 substrate.

Reply to Comment on ‘Modelling the magnetic dipole’

The claim that the model of a pair of fictitious magnetic charges, described in our recent paper, is that of an infinitely thin solenoid is a mistake, mainly based on misinterpretation of certain figures therein.