Congratulations to Kai Wu and co-workers! Their joint work “Characterizing Physical Properties of Superparamagnetic Nanoparticles in Liquid Phase Using Brownian Relaxation” published in Small was selected as Back Cover in volume 13, issue 22 (Small 22/2017).

The nonlinear magnetic response of SPIONs to magnetic fields induces harmonic signals that contain information of these nanoparticles. In this paper, Kai Wu, Jian-Ping Wang and co-workers, report using the phase lag and harmonic ratios in the SPIONs to analyze the saturation magnetization, average hydrodynamic size, the dominating relaxation processes of SPIONs, and the distinction between single- and multi-core particles.