Fig. 4: Parameters of the RF relaxations.

Temperature dependences of the real (a) and imaginary (b) parts of the dielectric permittivity of Ba_1−xPb_xFe₁₂O₁₉, x = 0.2, measured for polarization \(E \bot c\) at different frequencies (solid lines). The crosses in b show results at 0.95 MHz as measured in a different set-up and for a sample with different geometry and electrodes. The Roman numerals denote the four detected relaxation processes (extrinsic: I and II; intrinsic: III and IV). The comparison between the data obtained on different samples utilizing different set-ups clearly illustrates the intrinsic character of relaxations III and IV (see text). c, d show Arrhenius plots of the temperature dependences of the relaxation times that correspond to the relaxational excitations observed in the low-frequency complex dielectric permittivity spectra of Ba_1−xPb_xFe₁₂O₁₉ with x = 0.2. The values correspond to the four peaks I–IV seen in the ε″(ν,T) data (b and Fig. 3). The closed spheres were deduced from fits of the ε′(ν) and ε″(ν) spectra (Fig. 3), whereas the open symbols were derived from the temperature-dependent data of b and Fig. SI6–2, which only provided an estimate of τ. The straight lines evidence a temperature-activated behavior with the activation energies as indicated. The temperature dependences of the dielectric strengths of relaxations I–III are shown in e, f. The dashed lines are guides to the eye.