Spin orientation evolution of individual ferromagnetic nanoparticle during reversing magnetization processes revealed by micromagnetic simulations

Abstract

Understanding the internal magnetization structure of an individual ferromagnetic nanoparticle (MNP) is crucial for deciphering its magnetic characteristics. Unfortunately, while certain techniques can measure the magnetic properties of an individual MNP, they fall short of accurately detecting the internal magnetization structure. In this work, micromagnetic simulations were employed to construct the internal magnetization structure of an individual CoFe2O4 (CFO) nanopyramid, and the energy jump behavior during the magnetization process was successfully explained, with simulation results aligning with dynamic cantilever magnetometry (DCM) experimental outcomes. Subsequently, the external stray field of the nanopyramid was simulated, and the stray field gradient map revealed distinct bright and dark regions corresponding to the reverse and forward saturation magnetizations of the CFO nanopyramid. This result is possible to be verified by magnetic force microscopy (MFM) measurements of individual CFO nanopyramids. The confidence in the accuracy of the simulated internal magnetization structure was significantly enhanced by independently verifying the micromagnetic simulation results through DCM and MFM experiments. Our work proposes a convenient and cost-effective method for studying the internal magnetization structure of individual MNPs.