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Nonlinear Dynamic Hysteresis Driven Self-Heating in Fe100-xCox Alloy Nanoparticles
Gongotree Phukan1, Abegail1, Mritunjoy Prasad Ghosh2
1Nanomagnetism Lab, Department of Physics, National Institute of Technology Nagaland, Chumukedima, Nagaland 797103, India.
Langmuir : the ACS Journal of Surfaces and Colloids
|May 13, 2026
Summary
Stoichiometric variation of iron-cobalt alloy nanoparticles (NPs) was studied for self-heating performance. Fe50Co50 NPs demonstrated superior magnetic properties and high specific absorption rate (SAR) for magnetic hyperthermia applications.
Area of Science:
- Materials Science
- Nanotechnology
- Biomedical Engineering
Background:
- Iron-cobalt (FeCo) alloy nanoparticles (NPs) are promising for magnetic hyperthermia due to their magnetic properties.
- Optimizing FeCo NP composition is crucial for enhancing self-heating efficiency under alternating magnetic fields (AMF).
Purpose of the Study:
- To investigate the correlation between the composition of hydrothermally synthesized Fe100-xCox NPs, their magnetic anisotropy, and self-heating performance under AMF.
- To determine the optimal FeCo composition for efficient heat generation in magnetic hyperthermia.
Main Methods:
- Hydrothermal synthesis of Fe100-xCox NPs with varying stoichiometry (x = 35, 45, 50, 55, 65).
- X-ray diffraction (XRD) for structural analysis.
- Vibrating Sample Magnetometry (VSM) for magnetic characterization (saturation magnetization, anisotropy constant).
- Induction heating experiments under clinically relevant AMF conditions (14.98 kA/m, 337 kHz) to measure specific absorption rate (SAR).
Main Results:
- All samples formed a disordered BCC solid solution phase, suitable for high saturation magnetization.
- Equiatomic Fe50Co50 composition exhibited the highest saturation magnetization (Ms) and anisotropy constant, leading to the largest anisotropy energy barrier.
- Fe50Co50 NPs achieved a maximum SAR of 291 W/g, outperforming conventional ferrites.
- A direct linear relationship was observed between SAR and anisotropy energy barrier (ΔE), indicating nonlinear heat generation processes (dynamic hysteresis losses) in the high field regime.
Conclusions:
- The study highlights the critical role of magnetic anisotropy in dictating the self-heating performance of FeCo NPs under AMF.
- Fe50Co50 composition is identified as an ideal candidate for magnetic hyperthermia and other field-driven applications due to its superior magnetic properties and high SAR.
- Maximizing thermal performance in high field regimes requires a large effective anisotropy barrier, achieved through optimized composition and understanding of nonlinear heating mechanisms.
