Emergent magnetic properties of biphase iron oxide nanorods

We report on the magnetic properties of biphase iron oxide nanorods (NRs) consisting of ferrimagnetic Fe3O4 and antiferromagnetic alpha-Fe2O3 phases. Annealing as-prepared NRs at 250 degrees C for 5h, significantly improved the crystallinity of the Fe3O4 phase and enhanced the volume fraction of the alpha-Fe2O3 phase. Magnetometry data consistently reveal these two magnetically distinct phases, which are not in proximity to each other but separated by a region of disordered spins giving rise to enhanced magnetization at low temperatures when the sample was cooled down from 300 K in the presence of a 1T field to 10 K. This phenomenon which is also known as the pinning effect is much more pronounced in the annealed sample, resulting from the increased volume fraction of the alpha-Fe2O3 phase which could strengthen the interfacial spin frustration between these two phases and enhance the density of disordered spins at the interface. (C) 2022 Author(s).