Abstract Magnetic nanoparticles placed in a high frequency alternating magnetic field release heat. This phenomenon can be used to heat and kill cancerous cells, the so-called magnetic hyperthermia treatment. Our study focuses on the influence of the medium viscosity on the heating power of magnetic nanobeads (MNBs) containing superparamagnetic nanoparticles. The specific absorption rate (SAR) of two types of MNBs differing by their size was determined by measuring the area of their high-frequency hysteresis loops. Three different behaviors are observed as viscosity rises: (i) SAR first drops to a minimum value for both MNB sizes; (ii) interestingly, and only for smaller MNBs, after going through a minimum, SAR increases again towards a steady value; (iii) for larger MNBs, SAR remains constant after reaching its minimum value. The physical origin of these different behaviors is interpreted, the key ingredient to explain them being the magnetic interactions, the possibility of the bead to form chains, and their possibility to physically rotate under the influence of the magnetic field. Finally these results lead to questioning the representativeness of SAR measurements in water for nanoparticles intended for biological applications, in which the medium viscosity is very different from the one of water.

中文翻译：

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介质粘度对含磁性纳米颗粒的纳米珠加热功率和高频磁性能的影响

摘要 置于高频交变磁场中的磁性纳米粒子会释放热量。这种现象可以用来加热和杀死癌细胞，即所谓的磁热疗。我们的研究重点是介质粘度对含有超顺磁性纳米颗粒的磁性纳米珠 (MNB) 的加热功率的影响。两种尺寸不同的 MNB 的比吸收率 (SAR) 是通过测量其高频磁滞回线的面积来确定的。随着粘度的增加，观察到三种不同的行为：(i) SAR 首先下降到两种 MNB 尺寸的最小值；(ii) 有趣的是，仅对于较小的 MNB，在经过最小值后，SAR 再次增加到稳定值；(iii) 对于较大的 MNB，SAR 在达到最小值后保持不变。解释了这些不同行为的物理起源，解释它们的关键因素是磁相互作用、珠子形成链的可能性以及它们在磁场影响下物理旋转的可能性。最后，这些结果导致对用于生物应用的纳米颗粒在水中的 SAR 测量的代表性提出质疑，其中介质粘度与水的粘度非常不同。