LAUSR

High coercivity magnets are crucial in technology today, but dependence on rare earth elements and/or precious metals limits the application of the state of the art magnets. Here we introduce a method for producing large sized nanocomposite magnets comprised primarily of a metastable material. They have a very high coercivity (∼12 kOe) and are based on three of the most earth abundant elements—Fe, Si and O. The key is leveraging length scale and kinetic control to stabilize a large volume content of the metastable e-Fe2O3 nanophase in a thin silica matrix to obtain a high density of magnetic phase. X-ray diffraction, electron microscopy and magnetic measurements confirm densely packed nanorods consisting primarily of e-Fe2O3. These nanocomposites have some of the highest coercivities reported in dense millimeter-sized magnets that do not contain rare earths or precious metals.