Gaydamak T. Elastic characteristics of FeSe, SmFe3(BO3)4, NdFe3(BO3)4 and acoustoelectric transformation in them

The thesis is devoted to investigation of: sound velocities behavior at low temperatures, determination of the elastic modulus tensor components and research of the mechanisms of acoustoelectromagnetic and acoustoelectric transformations in FeSe, SmFe3(BO3)4 and NdFe3(BO3)4 single crystals. For FeSe single crystals, sound velocities have been measured and all components of the elastic modulus tensor have been determined. The structural and superconducting phase transitions influence on sound velocities and attenuation has been studied. The process of acoustoelectromagnetic transformation has been investigated. The intensive generation of electromagnetic radiation has been discovered and determined as piezomagnetism. The competency of the method has been confirmed on CoF2 single crystal. The experiments results coincide qualitatively and quantitatively with the well known ones of the direct static measurements. Sound velocities have been measured in of SmFe3(BO3)4 and NdFe3(BO3)4 singlecrystals, the tensor components of elastic and piezoelectric modulus have been determined. Giant magnetopiezoelectric effect has been revealed. The effect shows itself as the anomalously large growth of the effective piezomodulus below Neel temperature and its suppression by magnetic field.