Magnetization Reversal in Europium Sulfide Nanocrystals

We report the observation of the reversal in the magnetization hysteresis curve of europium sulfide nanocrystals. This phenomenon was investigated through the temperature-dependent magnetization of two classes of nanomaterials, nanocrystalline (2.0 nm \textit{$\le $ }d$_{NCs}$\textit{ $\le $ }100 nm), and quantum-confined (d$_{NCs}$\textit{ $\le $ }2.0 nm), where d$_{NCs}$ is the diameter of the nanomaterial. The effect of the size of the nanomaterial on the magnetization is attributed to the competition between the magnetic properties of strained surface atoms and unstrained core atoms. Superconducting quantum interference device (SQUID) probed the magnetic response. Electron microscopy and X-ray diffraction spectroscopy revealed the crystallinity and monodispersivity of the nanomaterials.