Investigation of the dynamic magnetic properties in RuO₂/Co-Fe-B stack film

We present the research on the fabrication of RuO 2 and the change in dynamic magnetic properties of RuO 2 /Co-Fe-B stack films with different thicknesses of the RuO 2 layer ( t RuO2 ) and the Co-Fe-B layer ( t CFB ). The RuO 2 film with a three-domain structure was oriented in (100) direction with a large strain on the α-Al 2 O 3 (0001) substrate. The film formation with an atomically flat surface morphology was observed. Through ferromagnetic resonant measurements on RuO 2 /CFB samples, we found that the effective magnetization (4π 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 (α) increases with the decrease of t CFB from 0.0056 at t CFB = 10 nm to 0.022 at t CFB = 1.2 nm. On the other hand, 4π M s, eff and α are independent of t RuO2 which would relate to the small spin-orbit coupling in RuO 2 . The results would be helpful for the ongoing research and application of altermagnet-based spintronics utilizing RuO 2 .