Temperature dependence of the effective magnetic anisotropy field and ferromagnetic resonance linewidth in polycrystalline complex substituted magnetically uniaxial hexagonal ferrites in the frequency range of 25 – 67 GHz

Temperature dependences of the effective magnetic anisotropy field and ferromagnetic resonance linewidth in samples of isotropic and anisotropic hexaferrite SrFe$_{11.2}$Al$_{0.1}$Si$_{0.15}$Ca$_{0.15}$O$_{19}$ and anisotropic hexaferrite BaFe$_{10.4}$Al$_{1.4}$Si$_{0.15}$Mn$_{0.1}$O$_{19}$, obtained by ceramic technology with wet blanks pressed in the magnetic field of 10 kOe, were studied in the frequency range from 25 to 67 GHz. The studies were carried out at temperatures from 25 to 85$^\circ$C. The change in the magnetic anisotropy in this temperature range was found to be 9.8 Oe/$^\circ$C for barium hexaferrite and 4.2 Oe/$^\circ$C for strontium hexaferrite; the change in the ferromagnetic resonance linewidth was 12.2 Oe/$^\circ$C for barium hexaferrite and 10 – 12.3 Oe/$^\circ$C for strontium hexaferrite.