Lorentz transmission electron microscopy on nanometric magnetic bubbles and skyrmions in bilayered manganites La_(1.2)Sr_(1.8)(Mn_(1-y)RU_y)_2O_7 with controlled magnetic anisotropy

摘要

We have investigated nanometric magnetic textures in thin (＜150nm) plates of Ru-doped bilayered manganites La_(1.2)Sr_(1.8)(Mn_(1-y)Ru_y)_2O_7. Ru substitution for Mn site changes the magnetic anisotropy from in-plane to out-of-plane easy axis type without any significant change of global magnetic and crystal structures. The combination of conventional and Lorentz transmission electron microscopy observations confirms the emergence of magnetic bubbles and skyrmions in the absence of magnetic field. With the changing Ru concentration, systematic changes in the type of magnetic bubbles are observed. A tiny residual magnetic field also affects the generation and the type-change of magnetic bubbles.