Ferrimagnetic Skyrmions in A Tetragonal Mn _1.9 Co _0.1 Sb Single Crystal at Room Temperature

ABSTRACT The development of room temperature small‐sized ferrimagnetic skyrmion materials is significant for topological spintronic device applications. As a room temperature ferrimagnetic material, the tetragonal Mn _1.9 Co _0.1 Sb crystal exhibits multiple phase transitions, including spin reorientation transitions. However, the magnetic spin textures and their evolution mechanisms during magnetic phase transitions in Mn _1.9 Co _0.1 Sb crystals remain unexplored. Using Lorentz transmission electron microscopy, we discovered and verified dipolar skyrmion behavior and its magnetic evolution at room temperature. We established a stable phase diagram of magnetic textures as functions of temperature and magnetic field, while also investigating the evolution mechanisms of spin textures across multiple temperature‐induced magnetic phase transitions. Through micromagnetic simulations, a ferrimagnetic configuration with in‐plane ferromagnetic coupling and interlayer antiferromagnetic arrangement was established, which stands in contrast to synthetic ferrimagnetic/antiferromagnetic systems that exhibit interlayer antiferromagnetic coupling via the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction. We determined that the intrinsic frequency of ferrimagnetic skyrmions can reach the THz regime due to strong interlayer antiparallel exchange interactions. These findings highlight the diversity of room temperature ferrimagnetic skyrmion regulation behaviors in Mn _1.9 Co _0.1 Sb and their dynamic evolution characteristics, opening new avenues for developing ultrafast skyrmionic devices with enhanced functionalities capable of operating under ambient conditions.