Investigation of the Dynamic Magnetic Properties in RuO2/Co-Fe-B Stack Film

We present the research on the fabrication of RuO2 and the change in dynamic magnetic properties of RuO2/Co-Fe-B stack films with different thicknesses of RuO2 layer (t(RuO2)) and Co-Fe-B layer (t(CFB)). RuO2 film with a three-domain structure was oriented in (100) direction with a large strain on alpha-Al2O3 (0001) substrate. The film formation with an atomically flat surface morphology was observed. Through ferromagnetic resonant measurements on RuO2/CFB samples, we found that the effective magnetization (4(pi)M(s,eff)) decreases as t(CFB) decreases which could be attributed to the contribution of the interfacial anisotropy energy. In addition, the damping constant (alpha) increases with the decrease in t(CFB) from 0.0056 at t(CFB) =10 nm to 0.022 at t(CFB) =1.2 nm. On the other hand, 4(pi)M(s,eff) and (alpha) are independent of t(RuO2) which would relate to the small spin-orbit coupling (SOC) in RuO2. The results would be helpful for the ongoing research and application of altermagnet-based spintronics using RuO2.