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 (
$t_{\text {RuO2}}$
) and Co-Fe-B layer (
$t_{\text {CFB}}$
). 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 (
$4\pi M_{\mathrm {s, eff}}$
) decreases as
$t_{\mathrm {CFB}}$
decreases which could be attributed to the contribution of the interfacial anisotropy energy. In addition, the damping constant (
$\alpha $
) increases with the decrease in
$t_{\mathrm {CFB}}$
from 0.0056 at
$t_{\mathrm {CFB}} =10$
nm to 0.022 at
$t_{\mathrm {CFB}} =1.2$
nm. On the other hand,
$4\pi M_{\mathrm {s, eff}}$
and
$\alpha $
are independent of
$t_{\mathrm {RuO2}}$
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.