Enhanced Magnetism in Highly Ordered Magnetite Nanoparticle-Filled Nanohole Arrays

A new approach to develop highly ordered magnetite (Fe3O4) nanoparticle‐patterned nanohole arrays with desirable magnetic properties for a variety of technological applications is presented. In this work, the sub‐100 nm nanohole arrays are successfully fabricated from a pre‐ceramic polymer mold using spin‐on nanoprinting (SNAP). These nanoholes a then filled with monodispersed, spherical Fe3O4 nanoparticles of about 10 nm diameter using a novel magnetic drag and drop procedure. The nanohole arrays filled with magnetic nanoparticles a imaged using magnetic force microscopy (MFM). Magnetometry and MFM measurements reveal room temperature ferromagnetism in the Fe3O4‐filled nanohole arrays, while the as‐synthesized Fe3O4 nanoparticles exhibit superparamagnetic behavior. As revealed by MFM measurements, the enhanced magnetism in the Fe3O4‐filled nanohole arrays originates mainly from the enhanced magnetic dipole interactions of Fe3O4 nanoparticles within the nanoholes and between adjacent nanoholes. Nanoparticle filled nanohole arrays can be highly beneficial in magnetic data storage and other applications such as microwave devices and biosensor arrays that require tunable and anisotropic magnetic properties. A simple, but efficient process to print and uniformly fill highly ordered sub‐100 nm nanoholes with monodispersed 10 nm Fe3O4 nanoparticles is demonstrated. Magnetization and magnetic force microscopy results confirm magnetism enhancement in these Fe3O4‐filled nanohole arrays compared to the as‐synthesized nanoparticles. The simplicity, low cost, and short processing time make this technique favorable for a variety of applications.