To meet the requirements for miniaturization and higher operating frequencies in self‑biased circulators, improving the performance of hexaferrite materials is essential. In this work, Sc-La-Zn co-substituted M-type barium ferrites (La_0.3Ba_0.7Fe_10.9–xZn_0.3Sc_xO₁₉) are prepared via solid-state reaction. X-ray diffraction (XRD) confirms the formation of a single-phase magnetoplumbite structure in all samples. Scanning electron microscopy (SEM) images shows that the ferrite particles have a hexagonal platelet morphology and are aligned along the c-axis after wet pressing and sintering under a magnetic field. Lattice parameters and particle sizes are calculated from the XRD and SEM data. Magnetic measurements indicate that the Sc-La-Zn substituted M-type ferrites have high saturation magnetization (M_s > 60 emu/g), and by controlling Sc doping, the magnetocrystalline anisotropy field can be adjusted between 7–10 kOe. Moreover, a narrow ferromagnetic resonance linewidth (ΔH ≈ 260 Oe) is achieved. Based on the measured magnetic parameters, three self-biased circulators operating at center frequencies from 25 GHz to 35 GHz are designed, simulated using HFSS, and demonstrate a broad frequency tuning range. The circulators exhibit a minimum insertion loss below 0.5 dB and a maximum isolation bandwidth (isolation >20 dB) of up to 4.4 GHz. This study demonstrates the potential of these materials in achieving self‑biased circulators capable of operating across different frequency bands.