Magnetic properties of aligned multiferroic Janus nanofiber agglomerates measured with the Scattered Magneto-Optical Kerr Effect

We report magnetic properties of electrospun multiferroic nanofibers assembled into linear aggregates with an external magnetic field, and measured with the Magneto-Optical Kerr Effect (MOKE) in a non-specular or scattering geometry (ScMOKE). Compared with bulk magnetometry, ScMOKE's sensitivity to subtle differences between aggregates offers a route to determine local multiferroic coupling in disordered nanomaterials. CoFe2O4-BaTiO2 nanofiber agglomerates are assembled prior to measurement by suspending and aligning the fibers in a transparent air-cured polyvinyl alcohol (PVA) solution. We detect the polarization change in light scattered from the fibers, collected at an off-specular angle in order to eliminate the background caused by substrate reflection. Averaged hysteresis loops from different aggregates show a variety of unique structures. For our optical spot size of 15 μm, multiple fibers, within a single agglomerate, are detected simultaneously, suggesting ScMOKE can distinguish local magnetization reversal fields that vary from fiber to fiber, as well as magnetic interactions between fibers.