Spin-reorientation transition induced magnetic skyrmion in Nd_2Fe_(14)B magnet

摘要

The easy axis of Nd_2Fe_(14)B is known to deviate from the c-axis when the temperature decreases to under the spin reorientation point T_(SR), 135 K. In this work, magnetic domain evolution in Nd_2Fe_(14)B was in situ observed by using Lorentz transmission electron microscopy at variable temperatures and magnetic fields. It appears that most inverse domains shrink to stripes and disappear suddenly to achieve the saturation state under a magnetic field, and the saturation field increases with the decreasing temperature due to the increased anisotropy. Magnetic bubbles with zero topological number are formed at temperatures higher than T_(SR), whereas magnetic skyrmions are found at temperatures around T_(SR) due to the spin reorientation. The tunable anisotropy and saturation magnetization at T_(SR) are the main causes of forming magnetic skyrmions. This finding exhibits the feasibility of generating skyrmions in the ordinary rare-earth permanent magnetic materials.