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<p>Lanthanum-modified strontium–nickel hexaferrite nanoparticles were produced using an auto-combustion sol–gel route to assess their potential as microwave absorbers. A set of compositions, Sr<sub>0.50</sub>Ni<sub>0.50</sub>La<sub>x</sub>Fe<sub>12−x</sub>O<sub>19</sub> (x = 0.00, 0.25, 0.35, 0.50), was synthesized to study how gradually replacing Fe with La influences the structural, magnetic, dielectric, and electromagnetic attenuation behavior. The successful formation of the M-type hexaferrite phase is verified by XRD patterns, showing only slight lattice variations caused by Ni presence, and crystallite dimensions ranging from 29 to 48&#xa0;nm. The FTIR spectra revealed characteristic metal–oxygen stretching vibrations corresponding to both tetrahedral and octahedral coordination sites, confirming the structural purity of the samples. Magnetic measurements obtained via VSM demonstrated that La substitution enhances the saturation magnetization, which increased from 50.66 to 59.29 emu/g. For x = 0.35, coercivity decreased significantly, dropping from 3956 Oe to 3110 Oe for x = 0.50 and further down to 2829 Oe, showing the evolution toward soft-magnetic behavior desirable for microwave-absorbing materials. The dielectric and magnetic responses, evaluated through the real and imaginary components of permittivity and permeability, showed that µ′ from 1.69 to 2.51 and ε′ increased from 4.23 to 8.64 at x = 0.35, revealing improved magnetic resonance effects and interfacial polarization. Among all prepared compositions, the x = 0.35 sample offered the most balanced electromagnetic properties, with ε′ = 11.84, ε″ = 5.16, µ′ = 2.73, and µ″ = 7.42 at 1&#xa0;GHz, validating its superior microwave attenuation performance. Reflection loss measurements in the X-band (8–12&#xa0;GHz) confirmed strong absorption for all samples, with the x = 0.35 composition showing the best result, a normalized impedance (Zin/Z0) close to 0.8, signalling excellent impedance matching at 9.45&#xa0;GHz with minimum RL of − 39.26 dB. These findings establish La-doped Sr–Ni hexaferrite nanoparticles as lightweight, adjustable, and highly effective candidates for stealth and electromagnetic shielding applications.</p>

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Structural and Electromagnetic Insights into Lanthanum-Substituted Strontium-Nickel (Sr–Ni) Hexaferrites for Enhanced X-Band Microwave Attenuation

  • 期刊论文

  • 发表日期：

    2026年2月18日

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  • Abdul Karim,
  • Iftikhar Hussain Gul

摘要

Lanthanum-modified strontium–nickel hexaferrite nanoparticles were produced using an auto-combustion sol–gel route to assess their potential as microwave absorbers. A set of compositions, Sr0.50Ni0.50LaxFe12−xO19 (x = 0.00, 0.25, 0.35, 0.50), was synthesized to study how gradually replacing Fe with La influences the structural, magnetic, dielectric, and electromagnetic attenuation behavior. The successful formation of the M-type hexaferrite phase is verified by XRD patterns, showing only slight lattice variations caused by Ni presence, and crystallite dimensions ranging from 29 to 48 nm. The FTIR spectra revealed characteristic metal–oxygen stretching vibrations corresponding to both tetrahedral and octahedral coordination sites, confirming the structural purity of the samples. Magnetic measurements obtained via VSM demonstrated that La substitution enhances the saturation magnetization, which increased from 50.66 to 59.29 emu/g. For x = 0.35, coercivity decreased significantly, dropping from 3956 Oe to 3110 Oe for x = 0.50 and further down to 2829 Oe, showing the evolution toward soft-magnetic behavior desirable for microwave-absorbing materials. The dielectric and magnetic responses, evaluated through the real and imaginary components of permittivity and permeability, showed that µ′ from 1.69 to 2.51 and ε′ increased from 4.23 to 8.64 at x = 0.35, revealing improved magnetic resonance effects and interfacial polarization. Among all prepared compositions, the x = 0.35 sample offered the most balanced electromagnetic properties, with ε′ = 11.84, ε″ = 5.16, µ′ = 2.73, and µ″ = 7.42 at 1 GHz, validating its superior microwave attenuation performance. Reflection loss measurements in the X-band (8–12 GHz) confirmed strong absorption for all samples, with the x = 0.35 composition showing the best result, a normalized impedance (Zin/Z0) close to 0.8, signalling excellent impedance matching at 9.45 GHz with minimum RL of − 39.26 dB. These findings establish La-doped Sr–Ni hexaferrite nanoparticles as lightweight, adjustable, and highly effective candidates for stealth and electromagnetic shielding applications.