Switching field characteristics of individual iron particles by MFM

The switching fields of individual iron particles used in magnetic recording have been measured using a Magnetic Force Microscopy (MFM) technique. It is found that as the particle diameters increase from 20 nm to 70 nm, the easy axis switching fields decrease from 2850 Oe to 1800 Oe. As the field angle increases, the switching fields increase monotonically and approach 5000 Oe at particle hard axis. A head-on multidomain state was observed after a particle had been magnetized by a 10K Oe field along hard axis. Micromagnetic calculations based on a chain of spheres model have been performed to simulate the switching mode which gives good agreement with experimental data. It is concluded that the switching process is best described by a fanning-like mode at small field angles