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<p>Magnetothermal energy dissipation in magnetic nanoparticles requires efficient heat generation under alternating magnetic fields (AMFs), yet the mechanistic relationship between magnetic anisotropy, interparticle dipolar interactions, and heating performance remains insufficiently defined. In this study, Fe<sub>3</sub>O<sub>4</sub> and CoFe<sub>2</sub>O<sub>4</sub> nanoparticles were synthesized via co-precipitation and systematically characterized to isolate the role of magnetic anisotropy in governing magnetothermal behavior. Field-emission scanning electron microscopy (FESEM) confirmed comparable mean particle sizes (41 nm), while X-ray diffraction (XRD) indicated crystallite sizes of 14 nm, consistent with the formation of spinel ferrite phases in both systems. Vibrating sample magnetometry (VSM) revealed similar saturation magnetization values (64 emu.g<sup>−1</sup>) but significantly different coercive fields (Hc ≈ 15 Oe for Fe<sub>3</sub>O<sub>4</sub> and ≈ 400 Oe for CoFe<sub>2</sub>O<sub>4</sub>), providing a controlled basis for anisotropy-driven comparison. First-order reversal curve (FORC) analysis resolved distinct magnetic phase characteristics: Fe<sub>3</sub>O<sub>4</sub> exhibited predominantly single-domain behavior with a narrow interaction field distribution (IFD ≈ 250 Oe) and a minor superparamagnetic fraction (10%), whereas CoFe<sub>2</sub>O<sub>4</sub> showed a broad multiphase coercivity distribution extending to 4000 Oe and a substantially wider IFD (2200 Oe), indicative of strong dipolar interactions and magnetic heterogeneity. AMF-induced heating measurements (f = 400 kHz, H = 50–400 Oe) demonstrated superior performance of Fe<sub>3</sub>O<sub>4</sub>, with specific loss power (SLP) values approximately 58% higher than those of CoFe<sub>2</sub>O<sub>4</sub> under equivalent conditions, reaching 450 W.g<sup>−1</sup> at the highest concentration. Power-law analysis (<i>n</i> = 2.49) indicated nonlinear field dependence of heat generation consistent with a mixed relaxation-hysteresis dissipation regime in predominantly blocked single-domain particles, with performance differences governed by anisotropy-controlled switching dynamics rather than morphology or magnetization. Concentration-dependent measurements further revealed continuous SLP enhancement for Fe<sub>3</sub>O<sub>4</sub> (1–22 mg.mL<sup>−1</sup>), whereas CoFe<sub>2</sub>O<sub>4</sub> exhibited saturation behavior above 10 mg.mL<sup>−1</sup> due to dipolar interaction effects. These results establish magnetic phase homogeneity and low coercivity as key design parameters for optimizing magnetothermal performance and demonstrate the effectiveness of FORC analysis as a predictive tool for engineering ferrite-based functional materials.</p>

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Magnetic anisotropy and dipolar interactions as determinants of magnetothermal performance in Fe3O4 and CoFe2O4 nanoparticles: insights from first-order reversal curve analysis

  • 期刊论文

  • 发表日期：

    2026年5月13日

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  • Maan Al-Nuaim,
  • Hashim Jabbar,
  • Kamran Heydaryan,
  • Anwar A. Jumaa,
  • N. A. Abdullah,
  • Sumaia H. Gatia,
  • Saad Shaker Hussein,
  • Najat A. Hussain

摘要

Magnetothermal energy dissipation in magnetic nanoparticles requires efficient heat generation under alternating magnetic fields (AMFs), yet the mechanistic relationship between magnetic anisotropy, interparticle dipolar interactions, and heating performance remains insufficiently defined. In this study, Fe3O4 and CoFe2O4 nanoparticles were synthesized via co-precipitation and systematically characterized to isolate the role of magnetic anisotropy in governing magnetothermal behavior. Field-emission scanning electron microscopy (FESEM) confirmed comparable mean particle sizes (41 nm), while X-ray diffraction (XRD) indicated crystallite sizes of 14 nm, consistent with the formation of spinel ferrite phases in both systems. Vibrating sample magnetometry (VSM) revealed similar saturation magnetization values (64 emu.g−1) but significantly different coercive fields (Hc ≈ 15 Oe for Fe3O4 and ≈ 400 Oe for CoFe2O4), providing a controlled basis for anisotropy-driven comparison. First-order reversal curve (FORC) analysis resolved distinct magnetic phase characteristics: Fe3O4 exhibited predominantly single-domain behavior with a narrow interaction field distribution (IFD ≈ 250 Oe) and a minor superparamagnetic fraction (10%), whereas CoFe2O4 showed a broad multiphase coercivity distribution extending to 4000 Oe and a substantially wider IFD (2200 Oe), indicative of strong dipolar interactions and magnetic heterogeneity. AMF-induced heating measurements (f = 400 kHz, H = 50–400 Oe) demonstrated superior performance of Fe3O4, with specific loss power (SLP) values approximately 58% higher than those of CoFe2O4 under equivalent conditions, reaching 450 W.g−1 at the highest concentration. Power-law analysis (n = 2.49) indicated nonlinear field dependence of heat generation consistent with a mixed relaxation-hysteresis dissipation regime in predominantly blocked single-domain particles, with performance differences governed by anisotropy-controlled switching dynamics rather than morphology or magnetization. Concentration-dependent measurements further revealed continuous SLP enhancement for Fe3O4 (1–22 mg.mL−1), whereas CoFe2O4 exhibited saturation behavior above 10 mg.mL−1 due to dipolar interaction effects. These results establish magnetic phase homogeneity and low coercivity as key design parameters for optimizing magnetothermal performance and demonstrate the effectiveness of FORC analysis as a predictive tool for engineering ferrite-based functional materials.