  Magnetic skyrmions are promising for next-generation information storage and
processing owing to their potential advantages in data storage density,
robustness, and energy efficiency. The magnetic multilayers consisting of Pt,
Co, and a third metal element $X$ provide an ideal platform to study the
skyrmions due to their highly tunable magnetic properties. Here, we report the
observation of room-temperature bubble-like N\'eel skyrmions in epitaxial
Pt/Co/Cu multilayers in samples with multidomain states in zero field. The
magneto-optic Kerr effect (MOKE) and superconducting quantum interference
device (SQUID) magnetometry are applied to investigate the shapes of the
hysteresis loops, the magnetic anisotropy, and the saturation magnetization. By
tuning the Co thickness and the number of periods, we achieve perpendicular and
in-plane magnetized states and multidomain states that are identified by a
wasp-waisted hysteresis loop. Skyrmions are directly imaged by magnetic force
microscopy (MFM) and Lorentz transmission electron microscopy (LTEM). The
development of room-temperature skyrmions in Pt/Co/Cu multilayers may lead to
advances in skyrmion-related research and applications.
