Coupling electric and magnetic dipoles within nanoscale building blocks offers a promising strategy for creating hybrid materials with coupled magnetic and electric functionality. Here, we demonstrate a proof-of-concept approach for realizing this concept in Janus nanoparticles through surface-selective hybridization of ferrimagnetic barium hexaferrite nanoplatelets, selectively hybridized on one basal plane with organic polar ligands bearing a large electric dipole and a phosphonic anchoring group. The resulting Janus magneto-electric nanohybrids exhibit magnetic and electric dipoles oriented normal to the nanoplatelet basal plane. Surface-selective hybridization is achieved through a solid–liquid interfacial processing route involving magnetically directed monolayer assembly of nanoplatelets, selective ligand hybridization on the exposed basal plane, and subsequent harvesting of the modified particles. To probe the coupled dipolar response of these hybrids, we introduce multidipole electrophoresis in a magnetic field, a new experimental method that enables simultaneous interrogation of electric and magnetic dipolar interactions in colloidal nanoparticles. Optical measurements reveal external field-induced birefringence consistent with dual dipolar sensitivity. These results demonstrate a viable approach for engineering Janus magneto-electric nanostructures and provide a platform for exploring external field sensing in colloidal systems.
