Hypersound spin-wave resonances in strained crystal of iron borate

Antiferromagnets (AF) and simultaneously “weak” ferromagnets with anisotropy of the “easy plane” tape, such as hematite (a-Fe₂O₃) and iron borate (FeBO₃), possessesa number of the unique characteristics. Their high Neel´s temperature and a tremendous effective uniform exchange fieldresult in a strong magnetoelastic (ME) coupling. Due to above reasons, the peculiarities of dynamic effects of ME coupling in the iron borate present a physical interest, as the dynamic and static elastic deformations can change the magnetic properties of the crystal.In the direction of longitudinal sound propagation q ∥ C₃ ( q - is the sound wave vector, C₃ - is the threefold axis normal to the {111} basal “easy plane” of crystal)the ME coupling is due to a piezomagnetic (PM) mechanism [1], and a magnetostriction coupling between the longitudinal elastic oscillations along C₃ and magnetic subsystem is negligibly small due to a large energy gap for the high-frequency branch of spin-wave spectrum.At propagation of longitudinal hypersound wave along the axis of symmetry C₃ of FeBO₃ crystal in the magnetic field, the oscillation structures (OS) of amplitude and phase of a transmission coefficienthave been found out, and the physical model of that phenomenon was offered by us [2]. The idea is that in the mode of standing sound wave, a magnetic modulation (incommensurable) structure (MMS) there can be in a sample. In present work the frequency dependence of the resonances observed is experimentally investigated in the external magnetic field and their numerical simulation is conducted.