Microstructure and gyromagnetic properties of oriented polycrystalline W-type hexaferrite applied to a self-biased circulator at the K-band

The magnetic and structural characteristics of W-type hexaferrites (BaW) are explored to evaluate their potential use in a self-biased circulator. An orientation degree as high as 0.54 is obtained through magnetic field orientation. The corresponding remanence ratio M_r/M_s reaches 0.79, which is beneficial for restraining low-field loss and reducing insertion loss of the circulator. Gd^3 +–Mg²⁺ substitution is introduced to tailor the magnetic properties of BaW for applications in different frequencies. When the substitution content x is 0.10, BaW achieves high saturation magnetization (M_s= 71.73 emu/g), high remanence ratio, high coercivity (H_c= 3809 Oe), and appropriate magnetocrystalline anisotropy field (H_a= 7935 Oe). The ferromagnetic resonance (FMR) is successfully detected with a linewidth of 962 Oe at 44 GHz. Based on this adjusted BaW material, a double Y-junction self-biased circulator with well K-band circulation is designed.