Ferromagnetic resonance (FMR) measurements, often referred to as electron magnetic resonance (EMR) when measurements are performed on magnetic nanoparticles, can be used to determine the magnetic moment distribution and the magnetic anisotropy of nanoparticles. The measurements are typically performed at different temperatures in spectrometers used for X-band (9 GHz) and/or Q-band (34 GHz) experiments. A typical spectrum obtained for iron-oxide nanoparticles with sizes < 15 nm exhibits a two-component line shape; a broad line with approximately Gaussian shape and a narrow line superimposed on the broad line. Interestingly, results from measurements on larger nanoparticles indicate that the narrow line is absent for larger nanoparticles, which suggests that the narrow line may be assigned to spin disorder at the surface of the nanoparticles. The analysis of an EMR spectrum includes line shape, resonant field and peak-to-peak line width. Several methods have emerged to address spectral trends, e.g. line shape analysis to determine the magnetic moment distribution and resonant field shifts to extract information on magnetic anisotropy energies.

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	This project has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 604448