Stable skyrmion bundles at room temperature and zero magnetic field in a chiral magnet

Topological spin textures are characterized by magnetic topological charges, Q , which govern their electromagnetic properties. Recent studies have achieved skyrmion bundles with arbitrary integer values of Q , opening possibilities for exploring topological spintronics based on Q . However, the realization of stable skyrmion bundles in chiral magnets at room temperature and zero magnetic field — the prerequisite for realistic device applications — has remained elusive. Here, through the combination of pulsed currents and reversed magnetic fields, we experimentally achieve skyrmion bundles with different integer Q values — reaching a maximum of 24 at above room temperature and zero magnetic field — in the chiral magnet Co 8 Zn 10 Mn 2 . We demonstrate the field-driven annihilation of high- Q bundles and present a phase diagram as a function of temperature and field. Our experimental findings are consistently corroborated by micromagnetic simulations, which reveal the nature of the skyrmion bundle as that of skyrmion tubes encircled by a fractional Hopfion. Manipulation of topological charge at room temperature is a key tenet of skyrmionics. Here, the authors demonstrate tunable topological charges in skyrmion bundles at room temperature and zero magnetic field.