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<p>In this work, we report the observation of damped oscillations in the magnetic interactions of Fe<sub>3</sub>O<sub>4</sub>/polyaniline (PANI) nanocomposites. The oscillatory behavior is revealed through analysis of the magnetic interaction parameter Δm(H), obtained from isothermal remanent magnetization (IRM) and direct current demagnetization (DCD) measurements performed using vibrating sample magnetometry. Δm(H) exhibits alternating positive and negative values as a function of the applied magnetic field, indicating periodic switching between magnetizing and demagnetizing interaction regimes. The oscillation amplitude is on the order of 10<sup>–3</sup>–10<sup>–1</sup> (a. u.) and is centered around Δm (H) ≈ 0. We show that these oscillations emerge only within a narrow temperature window (≈ 330 ± 5&#xa0;K) and for specific ultraviolet (UV) exposure times, suggesting a thermally activated, chemically mediated mechanism. The experimental data are successfully described using a damped harmonic oscillator model, where dissipation and gain terms correspond to competing magnetic interaction processes. We attribute the oscillatory behavior to valence-driven modulation of the Fe<sup>2+/</sup>Fe<sup>3+</sup> mixed-valence system, activated by charge-transfer processes at the Fe<sub>3</sub>O<sub>4</sub>/PANI interface.</p>

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Observing damped oscillations in the magnetic interactions in Fe3O4/PANI nanostructures

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  • 发表日期：

    2026年3月10日

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  • Giovanna Celly,
  • André José,
  • Luana Hildever,
  • Monalisa Cavalcante,
  • José Holanda

摘要

In this work, we report the observation of damped oscillations in the magnetic interactions of Fe3O4/polyaniline (PANI) nanocomposites. The oscillatory behavior is revealed through analysis of the magnetic interaction parameter Δm(H), obtained from isothermal remanent magnetization (IRM) and direct current demagnetization (DCD) measurements performed using vibrating sample magnetometry. Δm(H) exhibits alternating positive and negative values as a function of the applied magnetic field, indicating periodic switching between magnetizing and demagnetizing interaction regimes. The oscillation amplitude is on the order of 10–3–10–1 (a. u.) and is centered around Δm (H) ≈ 0. We show that these oscillations emerge only within a narrow temperature window (≈ 330 ± 5 K) and for specific ultraviolet (UV) exposure times, suggesting a thermally activated, chemically mediated mechanism. The experimental data are successfully described using a damped harmonic oscillator model, where dissipation and gain terms correspond to competing magnetic interaction processes. We attribute the oscillatory behavior to valence-driven modulation of the Fe2+/Fe3+ mixed-valence system, activated by charge-transfer processes at the Fe3O4/PANI interface.