  Magnetic chiral skyrmion bubbles and achiral bubbles are two independent
magnetic domain structures, in which the former with equivalent winding number
to skyrmions offers great promise as information carriers for further
spintronic devices. Here, in this work, we experimentally investigate the
generation and annihilation of magnetic chiral skyrmion bubbles and achiral
bubbles in the Mn-Ni-Ga thin plate by using the Lorentz transmission electron
microscopy (L-TEM). The two independent magnetic domain structures can be
directly controlled after the field cooling manipulation by varying the titled
angles of external magnetic fields. By imaging the magnetization reversal with
increasing temperature, we found an extraordinary annihilation mode of magnetic
chiral skyrmion bubbles and a non-linear frequency for the winding number
reversal. Quantitative analysis of such dynamics was performed by using L-TEM
to directly determine the barrier energy for the magnetization reversal of
magnetic chiral skyrmion bubbles.
