Observation of magnetic structures in Fe granular films by differential phase contrast scanning transmission electron microscopy

Abstract

Differential phase contrast (DPC) scanning transmission electron microscopy was applied to investigate the magnetic structures of Fe granular films. The DPC images showed a cluster-like contrast of 200 nm in the lateral size, which could not be observed by Lorentz transmission electron microscopy in the Fresnel mode. The magnetization vector map reproduced from the DPC images indicated that a magnetization loop generally intersects several isolated particles of 20–40 nm in diameter. The films composed of densely dispersed magnetic particles showed larger magnetization loops, while more separately dispersed films tended to have smaller loops, or magnetization closures in one particle. The loop size is associated with the strength of magnetic interaction between magnetic particles.