First-Order Reversal Curve Analysis of Superparamagnetic Nanoparticles with Oriented Easy Axis of Magnetization

We analyzed the magnetization process of magnetic nanoparticles using first-order reversal curve (FORC) analysis and verified a superparamagnetic feature and the orientation of the easy axis of the particles. The FORCs and FORC diagram of magnetic nanoparticles dispersed in water exhibited a superparamagnetic feature. The differences in the magnetizations and distributions of the coercive force of the solid-state samples were used to identify the orientation of the easy axes of magnetization.