Hybridized propagating spin waves in a CoFeB/IrMn bilayer

In this work, we report the propagating spin waves hybridized between first-order and quasiuniform modes in a Co20Fe60B20 thin film capped by Ir25Mn75. The anticrossing gaps are observed at room temperature both in the reflection and transmission spectra, where the coupling strength can be tuned by varying the value of the in-plane wave vector at which the dispersion curves cross. The key mechanism behind this feature is theoretically ascribed to the dipole-dipole interaction by a model which accounts for many features of our experimental results. The strong coupling with a cooperativity up to 2.0 is achieved with taking the dissipation rates of two coupled branches into account. A reference CoFeB sample without IrMn reveals that the interfacial pinning effect also plays a role in the magnon-magnon hybridization. Tunable hybridization of magnons may foster the field of magnonics in information processing.