Presently we evaluated the natural relaxation frequency of the spin angular momentum of Fe₃O₄ and hemozoin superparamagnetic (SP) nanoparticles in D₂O solutions in function of the sample temperature. The sample was composed of 1% H₂O in D₂O with dispersed Fe₃O₄ or hemozoin nanoparticles at variable number density. The natural relaxation frequencies are in the sub-MHz and MHz range for the Fe₃O₄ and hemozoin nanoparticles, respectively. We studied resonance heating of the same samples. We found that scanning the external magnetic field strength in a constant-frequency radio-frequency (RF) electromagnetic field, with its magnetic field component perpendicular to the external magnetic field, we obtain resonant heating at the magnetic field strength of 50 or 100 Gs for the RF excitation at 150 or 300 MHz, respectively. The measured resonance line has a Lorentzian form, with the heating amplitude dependent on the number density of SP nanoparticles, RF power and time. The resonance width correlates with the natural relaxation frequency of the spin angular momentum of the SP nanoparticles. We describe a theoretical model explaining the experimental results. As the achievable heating rate is directly proportional to the spin relaxation rate of the SP nanoparticles, we expect two orders of magnitude higher heating rates in suspensions based on water with natural isotopic composition.

目前，我们评估了D ₂ O溶液中Fe ₃ O ₄和血红蛋白超顺磁性（SP）纳米粒子的自旋角动量的自然弛豫频率与样品温度的函数关系。样品由D ₂ O中的1％H ₂ O和分散的Fe ₃ O ₄或血红蛋白纳米颗粒以可变的数密度组成。Fe ₃ O ₄的自然弛豫频率在亚MHz和MHz范围内和溶血素纳米颗粒。我们研究了相同样品的共振加热。我们发现，在恒定频率射频（RF）电磁场中扫描其磁场分量垂直于外部磁场的外部磁场强度时，我们获得了磁场强度为50或100 Gs的共振加热，用于分别在150或300 MHz下的RF激励。测得的共振线具有洛伦兹形式，其加热幅度取决于SP纳米颗粒的数量密度，RF功率和时间。共振宽度与SP纳米颗粒的自旋角动量的自然弛豫频率相关。我们描述了解释实验结果的理论模型。