EN
The main parameters of micromagnetic structure formation in a vicinity of a second order phase transition were determined experimentally and theoretically. The theoretical study was performed using micromagnetic approach. External magnetic field H_{c} of appearance of micromagnetic structure and micromagnetic structure period L_{c} were determined for (001)-oriented plate with uniaxial K_{u} and cubic K₁ magnetic anisotropy. The plate was saturated by the field applied in its plane. In the model we assumed that magnetization vector undergoes small deviations from equilibrium if magnetic field is slightly reduced. These deviations are periodic in nature: micromagnetic structure has a form of a plane wave. Dependences of H_{c} and L_{c} on an azimuthal angle of external magnetic field and on anisotropy constants K_{u} and K₁ were derived analytically in this work. Experimental studies of micromagnetic structure near the second order phase transition were conducted on (EuEr)₃(FeGa)₅O₁₂ (001)-oriented 50 μm thick ferrite-garnet plate with K_{u} = 5700 erg/cm³ and K₁=-3700 erg/cm³. Micromagnetic structure was revealed by means of magnetooptic Faraday effect. The in-plane field was increased up to 2000 Oe. Experimentally determined values of H_{c} and L_{c} were compared with theoretical estimates.