Structural and magnetic tailoring of Zn2+-Doped Y-type hexaferrites for advanced spintronic and microwave applications
Résumé
A comprehensive study was carried out on the structural and magnetic properties of Zn2+-doped Y-type hexaferrites Ba0.5Sr1.5Mo2-xZnxFe12O22 (x = 0.0, 0.1, 0.2) synthesized via the conventional solid-state reaction method. X-ray diffraction (XRD) confirmed the formation of a Y-type hexaferrite phase with space group R3/m, accompanied by minor secondary phases such as M-type hexaferrite and spinel ferrite. Microstructural analyses using SEM, TEM, and HRTEM revealed well-defined hexagonal grains with sizes ranging from 112.17 to 56.38 nm. Lattice parameter analysis showed a progressive increase in the c parameter and a decrease in the a parameter with increasing Zn2+ substitution, attributed to the larger ionic radius of Zn2+ (0.74 Å) compared to Mo6+ (0.62 Å), which induces internal lattice strain and distortion. Electron Spin Resonance (ESR) spectra at various microwave power levels exhibited an effective gyromagnetic ratio (geff) of ∼2.023 at 300 K, associated with Fe3+ S-state ions. Magnetic measurements revealed a systematic decrease in saturation magnetization (Ms) from 65.33 emu/g (x = 0.0) to 45.32 emu/g (x = 0.2), while coercivity (Hc) increased with Zn2+ content, indicating enhanced magnetic hardness. The divergence between field-cooled (FC) and zero-field-cooled (ZFC) magnetization curves highlights strong magnetic anisotropy and spin blocking at low temperatures, with the ferrimagnetic nature preserved under Zn2+ doping. Overall, these results demonstrate that Ba0.5Sr1.5Mo2-xZnxFe12O22 hexaferrites combine tunable magnetic properties with structural stability, making them potentially useful for future microwave and spintronic applications after further high-frequency characterization and microstructural optimization.
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