A comparative study of K_u-band absorption characteristics and analysis of structural properties of Ba_1-xGd_xFe₁₂O₁₉ (0.00≤x≤0.50) samples

The solid state method was utilized to prepare Ba_1-xGd_xFe₁₂O₁₉ (0.00 ≤ x ≤ 0.50) samples. The XRD (profile matching) data indicated the presence of additional impurity (Fe₂O₃ and Gd₃Fe₂Fe₃O₁₂) phases besides the M-type Ba_1-xGd_xFe₁₂O₁₉ phase for x > 0.10. The concentration of M-type phase decreased from 100 % (at x = 0.00) to 40.69 % (at x = 0.50). The XRD data hence shows the multiphase nature of these samples. FESEM data established average grain size ≈0.75 μm in x = 0.20 and 0.40 samples. VNA data shows that ε′ and μ′ spectra are complementary to each other. Highest K_u-band response (RL(dB)) has been observed for the x = 0.1 sample. For this sample a RL(dB) value ≈ −18.12 dB has been observed at 12.40 GHz. The x = 0.5 sample exhibits insufficient microwave response (RL(dB = - 9.79 > −10 dB). Highest bandwidth (≈4.43 GHz) has been observed for x = 0.30 sample. The RL(dB) data suggests effective microwave response for x ≤ 0.40 samples. Further, the RL(dB) data corroborates nicely with the impedance matching data. The varying values of C₀ parameter with frequency suggest that natural resonance is responsible for magnetic losses in these samples. The total shielding effectiveness of various samples varies between 16.90 dB (for x = 0.50) and – 19.44 dB (for x = 0.00).