Magnetization and relaxation dynamics of core-shell magnetic nanoparticles over broad temperatures and frequencies

Magnetic nanoparticles (MNP) are becoming increasingly important as a tracer for non-invasive, in vivo imaging (e.g. MPI¹), magnetic hyperthermia, and thermometry. For these applications, MNP tracers, observed under AC magnetic fields, are desired to exhibit large magnetization and thermosensitivity (temperature-dependent magnetization), factors which are governed by a complex set of parameters, including size, morphology, magnetic anisotropy, and saturation magnetization.² Under AC driving fields, MNP response is affected by complex relaxation dynamics spanning broad timescales from seconds to nanoseconds.³ For response optimization, we chose bi-magnetic nanoparticles with core-shell morphology since their magnetic properties are tunable via the antiferromagnetic exchange coupling of the two magnetic phases. Here, we present magnetic characterization results for our synthesized doped ferrite core-shell nanoparticles over a range of temperatures (250-330 K), magnetic field amplitudes (0-20 mT_RMS), and frequencies (DC-10 MHz) to quantify magnetic anisotropy, relaxation times, and hysteresis.

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[2] Anderson et al. Phys. Rev. B, 94, p. 1-8 (2016)
[3] Deissler et al. Med. Phys. 41, p. 012301, (2014)