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Article

The Role of Anisotropy in Distinguishing Domination of Néel or Brownian Relaxation Contribution to Magnetic Inductive Heating: Orientations for Biomedical Applications

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Laboratory of Magnetism and Magnetic Materials, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam
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Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam
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Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Street, Cau Giay District, Ha Noi 100000, Vietnam
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Graduate University of Science and Technology, 18 Hoang Quoc Viet Street, Cau Giay District, Ha Noi 100000, Vietnam
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Biophysics Group, Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
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Healthcare Biomagnetic and Nanomaterials Laboratories, University College London, 21 Albemarle Street, London W1S 4BS, UK
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Duy Tan University, K7/25 Quang Trung Street, Da Nang City 550000, Vietnam
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Authors to whom correspondence should be addressed.
Academic Editor: Victor M. Prida
Materials 2021, 14(8), 1875; https://doi.org/10.3390/ma14081875
Received: 24 February 2021 / Revised: 31 March 2021 / Accepted: 6 April 2021 / Published: 9 April 2021
(This article belongs to the Special Issue Magnetic Nanoparticles as High-Frequency Nano-Heaters)
Magnetic inductive heating (MIH) has been a topic of great interest because of its potential applications, especially in biomedicine. In this paper, the parameters characteristic for magnetic inductive heating power including maximum specific loss power (SLPmax), optimal nanoparticle diameter (Dc) and its width (ΔDc) are considered as being dependent on magnetic nanoparticle anisotropy (K). The calculated results suggest 3 different Néel-domination (N), overlapped Néel/Brownian (NB), and Brownian-domination (B) regions. The transition from NB- to B-region changes abruptly around critical anisotropy Kc. For magnetic nanoparticles with low K (K < Kc), the feature of SLP peaks is determined by a high value of Dc and small ΔDc while those of the high K (K > Kc) are opposite. The decreases of the SLPmax when increasing polydispersity and viscosity are characterized by different rates of d(SLPmax)/dσ and d(SLPmax)/dη depending on each domination region. The critical anisotropy Kc varies with the frequency of an alternating magnetic field. A possibility to improve heating power via increasing anisotropy is analyzed and deduced for Fe3O4 magnetic nanoparticles. For MIH application, the monodispersity requirement for magnetic nanoparticles in the B-region is less stringent, while materials in the N- and/or NB-regions are much more favorable in high viscous media. Experimental results on viscosity dependence of SLP for CoFe2O4 and MnFe2O4 ferrofluids are in good agreement with the calculations. These results indicated that magnetic nanoparticles in the N- and/or NB-regions are in general better for application in elevated viscosity media. View Full-Text
Keywords: magnetic heating; Néel & Brownian relaxation; particle anisotropy; polydispersity; ferrofluid viscosity magnetic heating; Néel & Brownian relaxation; particle anisotropy; polydispersity; ferrofluid viscosity
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MDPI and ACS Style

Nguyen, L.H.; Phong, P.T.; Nam, P.H.; Manh, D.H.; Thanh, N.T.K.; Tung, L.D.; Phuc, N.X. The Role of Anisotropy in Distinguishing Domination of Néel or Brownian Relaxation Contribution to Magnetic Inductive Heating: Orientations for Biomedical Applications. Materials 2021, 14, 1875. https://doi.org/10.3390/ma14081875

AMA Style

Nguyen LH, Phong PT, Nam PH, Manh DH, Thanh NTK, Tung LD, Phuc NX. The Role of Anisotropy in Distinguishing Domination of Néel or Brownian Relaxation Contribution to Magnetic Inductive Heating: Orientations for Biomedical Applications. Materials. 2021; 14(8):1875. https://doi.org/10.3390/ma14081875

Chicago/Turabian Style

Nguyen, Luu H., Pham T. Phong, Pham H. Nam, Do H. Manh, Nguyen T.K. Thanh, Le D. Tung, and Nguyen X. Phuc. 2021. "The Role of Anisotropy in Distinguishing Domination of Néel or Brownian Relaxation Contribution to Magnetic Inductive Heating: Orientations for Biomedical Applications" Materials 14, no. 8: 1875. https://doi.org/10.3390/ma14081875

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