Frequency Dependence of Initial Heat Generation in Granular Magnetite Nanoparticles
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Frequency Dependence of Initial Heat Generation in Granular Magnetite Nanoparticles Hyung Joon Kim Basic Materials & Chemicals R&D Center, LG Chem Research Park, Daejeon 34122, Korea
Sunghyun Yoon∗ Department of Physics, Gunsan National University, Gunsan 54150, Korea (Received 2 July 2020; accepted 6 July 2020) The frequency dependence of heat generation in granular magnetite nanoparticles was studied using vibrating sample magnetometry and the nanoTherics MagnethermTM hyperthermia testing system. First, the particle size and its distribution were obtained by fitting the M -H curve to the classical Langevin function weight-averaged with a modified log-normal size distribution function. Next, the ac power dissipation model for monodispersed nanoparticles was extended to the polydispersed case, and the volumetric heating rate was predicted as a function of the frequency of the applied field under the assumption of the N´eel relaxation mechanism. Finally, the temperature increase caused by the application of an ac magnetic field was measured experimentally at frequencies of 50, 112, 261, 335, 474 and 523 kHz, with the root-mean-squared field fixed to 250 Oe, and the results were compared with those from theoretical calculation. The frequency dependence of the initial heating rates was found to be in good agreement with the results predicted by using the polydispersed power dissipation model. Keywords: Magnetic nanoparticles, Magnetic hyperthermia, Specific loss power, Superparamagnetism, Particle size distribution DOI: 10.3938/jkps.77.293
I. INTRODUCTION During the last decade, the heating effects of magnetic nanoparticles under an alternating magnetic field have been the subjects of intensive studies as promising medical candidates for hyperthermia treatment, and they are now finding their way into practical and clinical applications [1–3]. As a prerequisite for commercialization, those applications require the ability for quantitative prediction of the physicochemical phenomena that underlie the materials [4]. The efficiency of heat generation is characterized by the specific loss power (SLP) of a nanoparticle system under an ac magnetic field. A wide range of studies have been carried out in order to achieve the optimum SLP for hyperthermia applications by unveiling the effects of the material’s composition [5– 8], the particle size and its distribution [9–11], the sample temperature [12], the magnetic anisotropy [13–15], the particle morphology and concentration [16], the field strength [17,18], or the surfactant coating [19] upon the efficiency of heat generation. Up to now, numerous studies have been mainly focused on ferrofluids, i .e., aqueous suspensions of biocompati∗ E-mail:
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pISSN:0374-4884/eISSN:1976-8524
ble, non-interacting magnetic nanoparticles. However, as an example, we might sometimes need to fill the heating agent into the cavity of a bone or a tooth in the form of a compact paste, for which a considerable interparticle interaction is inevitable. Thus we require a versatile strategy to achieve
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