Terahertz Optomagnetism: Nonlinear THz Excitation of GHz Spin Waves in Antiferromagnetic FeBO_{3}.

A nearly single cycle intense terahertz (THz) pulse with peak electric and magnetic fields of 0.5 MV/cm and 0.16 T, respectively, excites both modes of spin resonances in the weak antiferromagnet FeBO_{3}. The high frequency quasiantiferromagnetic mode is excited resonantly and its amplitude scales linearly with the strength of the THz magnetic field, whereas the low frequency quasiferromagnetic mode is excited via a nonlinear mechanism that scales quadratically with the strength of the THz electric field and can be regarded as a THz inverse Cotton-Mouton effect. THz optomagnetism is shown to be more energy efficient than similar effects reported previously for the near-infrared spectral range.

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

A comparative analysis of the Czjzek's and Maurer's 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 Maurer's model, in contrast to the Czjzek's model, provides satisfactory fits to experimental NMR spectra.

(11)B 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.

Laser excitation of lattice-driven anharmonic magnetization dynamics in dielectric FeBO3.

Femtosecond laser pulses trigger in dielectric FeBO3 coherent oscillations of the magnetic anisotropy followed by spins. The oscillations are driven by optically excited lattice vibrations strongly coupled to the magnetic system. Unlike the spin resonances, this mode is characterized by a very small damping ratio and can be easily pushed into an anharmonic regime.