Microwave-Assisted switching in CoCrPt granular medium under continuous microwave fields

We have fabricated a device for microwave-Assisted switching (MAS) experiments with perpendicularly magnetized CoCrPt-SiO₂ granular film with anisotropy field H_k = 18.8 kOe. The device was carefully designed to be able to apply a microwave field of 0.95 kOe in amplitude continuously, allowing direct evaluation of microwave-Assisted switching properties of the medium without any assumptions about time-dependent switching behavior. The coercivity of CoCrPt-SiO₂ medium linearly decreases with increasing microwave frequency, and the maximum coercivity reduction ratio reaches 80% for h_rf = 0.95 kOe at f_rf = 25 GHz after subtracting the effect of temperature rise due to microwave field application. The linear slope of coercivity against the frequency becomes steeper with increasing microwave field amplitude, which is a unique frequency and amplitude dependencies in granular media. Correlation length obtained by X-ray magnetic circular dichroism microscopy measurement decreases by applying a microwave field with higher frequency, suggesting that the magnetic clustering dimensions of the medium possibly depend on microwave frequency during microwave-Assisted switching.