EPR Study of Superparamagnetism in Mn$_{\mathrm{\mathbf{3}}}$\textbf{O}$_{\mathrm{\mathbf{4}}}$\textbf{ Nanoparticle Ensembles}

The superparamagnetic relaxation of Mn$_{\mathrm{3}}$O$_{\mathrm{4}}$ nanoparticles has been investigated using Electron Paramagnetic Resonance (EPR) measurements carried out at low temperatures, between 20 and 120 K, in an applied sweeping magnetic field of 0 to 6000 G. Two nanoparticle ensembles were used, having average particle sizes of 10 nm and 5 nm as determined from X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM).