Determination of dominating relaxation mechanisms from temperature-dependent Magnetic Particle Spectroscopy measurements

•Determination of dominating relaxation mechanisms from temperature-dependent spectra.•Comparison of Fokker–Planck simulations with experimental MPS data.•Sharp bends in harmonic spectra attributed to superimposing and coupled relaxation. Magnetic Particle Spectroscopy (MPS) is a characterization method for investigating the nonlinear properties of magnetic nanoparticles (MNP) using magnetic field strengths in the order of a few tens of millitesla. Its exploitation for particle characterization is of high significance for biomedical applications such as Magnetic Particle Imaging (MPI) and magnetic hyperthermia. Since the dynamic characteristics of MNP are influenced by both the Néel and the Brownian relaxation mechanism, harmonic spectra in MPS measurements are directly linked to ambient influences like temperature or viscosity of the surrounding medium. Experimental data of multiparametric measurements helps one to evaluate and validate mathematical models of dynamic particle magnetization. This contribution deals with the investigation of temperature-dependent harmonic spectra of different commercially available single-core and multi-core particle systems. It is shown, that dominating relaxation mechanisms can be determined from temperature-dependent MPS measurements.