Lorentz transmission electron microscopy observation of magnetic skyrmion-like clusters in a ferromagnetic oxide

Magnetic skyrmions, where the spin configuration is a vortexlike spin swirling, show intriguing phenomena such as the topological Hall effect, and motion under ultralow electric-current density, leading to new magnetic devices. In colossal magnetoresistive man-ganites, the possible presence of magnetic skyrmion-like structures has been discussed so far. Lorentz transmission electron microscopy (LTEM) has an advantage of being able to observe such local magnetization distributions in real space. We therefore used LTEM to directly observe magnetic clusters in manganites. In the LTEM images, possible magnetic skyrmion-like vortices are visualized and show the repeated reversal of magnetic chirality caused by thermal fluctuation. When two magnetic clusters locate near each other, the repeated magnetization reversal becomes fully synchronized. In addition, we developed the quantitative determination of the barrier energy for the magnetization reversal by LTEM only.