Critical scattering of electromagnetic waves on spin fluctuations in nonsaturated magnetic films under acoustic pump

The theoretical and experimental investigation of the microwave (MW) combination scattering on spin fluctuations (SF) in the yttrium iron garnet film under acoustic pump were pursued. MW frequency f≂3.5–4.1 GHz was well above spin wave spectrum at a preassigned magnetic field. At the external magnetic field range H0≂5–40 Oe one (or more) intensity peaks of MW scattering were observed. The positions of these peaks do not depend on MW and surface acoustic wave (SAW) amplitudes and frequencies and depend heavily on the magnetic field directions in a film plane. Because these phenomena were closely associated with the domain walls (DW) reorientation or at the domain structure transformations, e.g., at the flexural instability of DW, one may speculate that critical scattering of MW on SAW and SF was observed. Cross section for such scattering was calculated. In nonsaturated magnetic films the phenomena of MW scattering on SAW and spin fluctuations at high amplitudes of the MW and SAW were investigated as well. In the area of external magnetic fields H0≥250 Oe a stepped dependence of intensity of scattering MW was observed. There is no appropriate explanation of this effect now.