  Materials hosting magnetic skyrmions at room temperature could enable new
computing architectures as well as compact and energetically efficient magnetic
storage such as racetrack memories. In a racetrack device, information is coded
by the presence/absence of magnetic skyrmions forming a chain that is moved
through the device. The skyrmion Hall effect that would eventually lead to an
annihilation of the skyrmions at the edges of the racetrack can be suppressed
for example by anti-ferromagnetically-coupled skyrmions. However, avoiding
modifications of the inter-skyrmion distances in the racetrack remains
challenging. As a solution to this issue, a chain of bits could also be encoded
by two different solitons such as a skyrmion and a chiral bobber. The major
limitation of this approach is that it has solely been realized in B20-type
single crystalline material systems that support skyrmions only at low
temperatures, thus hindering the efficacy for future applications. Here we
demonstrate that a hybrid ferro/ferri/ferromagnetic multilayer system can host
two distinct skyrmion phases at room temperature. By matching quantitative
magnetic force microscopy data with micromagnetic simulations, we reveal that
the two phases represent tubular skyrmions and partial skyrmions (similar to
skyrmion bobbers). Furthermore, the tubular skyrmion can be converted into a
partial skyrmion. Such multilayer systems may thus serve as a platform for
designing skyrmion memory applications using distinct types of skyrmions and
potentially for storing information using the vertical dimension in a thin film
device.
