  In recent years, magnetic skyrmion-based spin-torque nano-oscillators (STNOs)
attract considerable interest for their prospect in future-generation
communication and spintronic technologies. However, some critical issues, which
hamper their practical applications, e.g., the long start-up time and variable
skyrmion gyration orbit, remain to be resolved. Here, we numerically
demonstrate a realization of a fixed-orbit STNO, which is based on an
interlayer-coupled meron-skyrmion (MS) pair other than a magnetic skyrmion. In
this STNO, the MS pair possesses a structurally defined, fixed orbit within a
broad range of driving current, even in the presence of random defects. The
output frequency range of the STNO based on an MS pair far exceeds that of the
STNO typically based on a single skyrmion. Moreover, the output frequency of
this STNO can be further elevated if more MS pairs are incorporated. Our
results reveal the nontrivial dynamics of the interlayer-coupled MS pair,
opening perspectives for the design and optimization of fundamental spintronic
devices.
