Reflection of electromagnetic waves from a surface Co0.94Fe0.122+Fe1.963+ O4 and FeBO3 in UHF region

Summary form only given. Experimental and theoretical dependencies of the electromagnetic waves reflection coefficient (R) from a single crystal surface of the conducting ferrite Co_0.94Fe_0.12 ²⁺Fe_1.96³⁺O₄ and the easy-plane antiferromagnet FeBO₃ on a metal base have been investigated. From the experiment, the frequency dependencies of the reflection coefficient from a surface of Co_0.94Fe_0.12 ²⁺Fe_1.96³⁺O₄ ferrite in the 8-12 GHz range for different magnitudes of external constant magnetic fields there is a minimum in which magnitude of the reflection coefficient decreases to 3 dB (≈50%). The reflection coefficient from a surface FeBO₃ in this UHF region is small (R≈-15 dB or 0.03) and has a minimum. The frequency of the minimum is strongly correlated with the magnitude of the magnetic field. Such dependencies of the reflection coefficient for these magnetic materials means that in the given frequency region a large increase of magnetic permeability in the area a ferromagnetic and quasi ferromagnetic resonance takes place. The theoretical investigation of the reflection coefficient for given substances based on a model of coupled electromagnetic, spin end elastic waves. To determining of spectrum of elementary vibration in considered magnetics was decided equations system which consist of Landau-Lifsitz equation, Maxwell equations and equations of elasticity theory together with the system of boundary conditions. The reflection coefficient was calculated by the formula R=|h_R/h₀|²,where h_R, h₀ denote the amplitudes of the reflected and dropped waves accordingly defined from the decision of the system boundary equations. Computation of the reflection coefficient on the model of coupled electromagnetic, spin end elastic waves was made numerically. It was shown that the theoretical dependencies of the reflection coefficient for Co_0.94Fe_0.12²⁺Fe_1.96³⁺ O₄ and FeBO₃ are very close to the experimental results