Magnetic and dielectric properties of Mn2+ and Nb5+-doped NiCuZn ferrites for K-band junction circulators

Abstract

Ni0.42-x/3Nbx/3Cu0.18Zn0.4MnxFe1.98−xO4−δ (x = 0–0.1) materials, possessing a high saturation magnetization, high dielectric constant, and narrow ferromagnetic resonance linewidth, were prepared via the solid-phase reaction method. The cation distribution, as well as the dielectric and gyromagnetic properties, were studied in detail. Mn2+ and Nb5+ incorporated in the lattice occupy tetrahedral site, causing the redistribution of cation and the reduction of A–B superexchange interaction. This leads to an increase in saturation magnetization followed by a decrease. The introduction of appropriate amounts of Mn2+ and Nb5+ ions reduces the magnetocrystalline anisotropy constant |K1| and thus reduces the ferromagnetic resonance linewidth (ΔH). Furthermore, high polarisability of Mn2+ and Nb5+ causes the increase in the dielectric constant of the ferrites. At x = 0.08, excellent gyromagnetic and dielectric properties, including a high dielectric constant (ε’ = 15.4@100 MHz), high saturation magnetization (4πMs = 4577 G), and narrow ferromagnetic resonance linewidth (ΔH = 129 Oe@9.55 GHz) for the NiCuZn ferrite, was achieved. Finally, a K-band microstrip circulator operating at 20.8 to 28 GHz was designed. The simulation showed that the isolation of the circulator in the working frequency band is greater than 20 dB, showing the potential of the prepared ferrites in microwave circulators.