C-Axis-Oriented Ba(ZnHf)_xFe_12−xO₁₉ M-Type Barium Hexaferrite with a High Squareness Ratio

In this study, a series of oriented Ba(ZnHf)_xFe_12−xO₁₉ (x = 0.04, 0.06, 0.08, 0.10, 0.12, and 0.14) were fabricated via a solid-state reaction. The wet orientation process was used to realize high orientation along the c-axis. X-ray diffraction patterns show that the pure phase formation for all samples was ensured. Moreover, Fourier transform infrared spectroscopy revealed that the characteristic absorption peak of octahedral ferrites tended to shift to the left, which indicated the success of the Zn²⁺-Hf⁴⁺ ions substitution. Scanning electron microscopy images exhibited grain realignment along the hexagonal crystallographic c-axis in the oriented samples. The saturation magnetization (M_s) and the remanence ratio (M_r/M_s) remained at high levels. Furthermore, the M_r/M_s was as high as 0.93 when x = 0.08. The Zn²⁺-Hf⁴⁺ replacement caused the magnetocrystalline anisotropy field (H_K) to decrease while maintaining the c-axis anisotropy. This study demonstrated the oriented M-type barium hexaferrite’s considerable potential in self-biased microwave device designs, including circulators working at low frequencies.