High-frequency hysteresis characterization of superparamagnetic particles

A magnetometer to characterize hysteresis loops of magnetic particles at 50 kHz with excitation field amplitudes up to 60 mT is described. The nonlinear and hysteretic responses of magnetic nanoparticles are exploited in applications such as medical imaging and hyperthermia treatment. In the recently developed tomographic imaging technique known as magnetic particle imaging (MPI), the image contrast relies on the nonlinear magnetization response of superparamagnetic iron oxide nanoparticle tracers [1]. In the treatment of cancer by hyperthermia, hysteresis losses in magnetic nanoparticles are used to generate localized heat in tumors [2]. In both applications, characterization of the nonlinear and hysteretic behavior of the particles would guide improvements in system performance and enable optimal nanoparticle synthesis methods to be developed [3].