Emergence of Magnetic Monopole-like Behavior in Iron Oxide Nanoparticles Grafted with Chiral Brushes: A Chiral Induced Spin Selectivity Manifestation

Abstract

We examine the magnetic properties of ~20 nm single domain and ~200 nm multidomain iron oxide nanoparticles that are surface functionalized with poly(L- or D-phenylalanine) chiral brushes of variable length. Interestingly, the larger nanoparticles manifest a remanent magnetization in all directions, i.e., display monopole-like or hedgehog behaviour that depends on the handedness of the brush. Conversely, no such response is observed in the smaller nanoparticles. The emergent monopole-like magnetic properties are attributed to the chiral-induced spin selectivity effect acting on the magnetic domain structure, single vs. multidomain, to imprint a magnetization bias on the nanoparticles. Collectively, this study reveals a facile approach for the formation of hedgehog magnetic nanoparticles and outlines features necessary for their formation.