Abstract:

With the increasing demand for highly integrated devices in 5G communication, the development of gyromagnetic ferrites combining high dielectric constant and low saturation magnetization has become a research focus. This study aims to design and prepare a garnet ferrite suitable for the 3.0-3.6 GHz band through a multi-ion co-substitution strategy. A series of Bi_1.4Gd_0.2Ca_1.4Zr_0.2Al_nV_0.6Fe_4.2-nO₁₂ (n=0-0.20) samples were synthesized by the solid-state reaction method. The effects of Al³⁺ substitution on the microstructure, magnetic properties, and dielectric properties were systematically investigated. All samples maintain a pure garnet phase without secondary phases. Dense and uniform microstructures with clear grain boundaries are observed. The results show that the optimal comprehensive performance is achieved at n=0.10: the saturation magnetization (4πM_s) is significantly reduced to 774 G (1 G=10^-4 T), the ferromagnetic resonance linewidth (ΔH) is optimized to 83 Oe (1 Oe=1000/4π A/m≈ 79.577 A/m), the dielectric constant (ε_r) reaches 26.31, and the dielectric loss (tanδ_ε) is as low as 8.49×10^-4. A dual-Y-junction circulator fabricated based on this optimized material exhibits excellent microwave performance within the 3.0-3.6 GHz band, with an insertion loss of 0.27 to 0.31 dB, return loss and isolation both better than 20 dB. Moreover, the device demonstrates stable performance over a wide temperature range from -40 ℃ to 85 ℃, indicating its reliability for practical engineering applications. The Al³⁺ substitution synergistically reduces both 4πM_s and ΔH by diluting magnetic ions and weakening magnetocrystalline anisotropy. This work provides a high-performance ferrite material solution for miniaturized 5G circulators and contributes to the advancement of integrated microwave devices for next-generation communication systems.

Key words: gyromagnetic ferrite, circulator, Bi-YIG, low saturation magnetization