Perpendicular Magnetic Anisotropy Dependence of Exchange Spin Resonance Mode for Ferrimagnetic GdCoFe Nanoscale Thin Films: Implications for High-Speed Spintronic Devices

Both the ferromagnetic and exchange resonance modes were investigated in the ferrimagnetic Gd x (Co 80 Fe 20 ) 100– x nanoscale thin films by using an all-optical pump–probe technique. We observed that the ferromagnetic resonance frequency f FMR significantly increases in the vicinity of the angular momentum compensation point C A as well as the effective g -factor g eff and Gilbert damping parameter α s, which could be fitted well with the theoretical calculation by the Kittel equation. Unconventionally, the exchange resonance mode only appears in the range of 25 at. % ≤ x ≤ 27 at. % (Gd-rich) near C A . The exchange resonance frequency f exch shows a monotonic increase with increasing perpendicular anisotropy constant K z . We report the experimental and theoretical investigations that the f exch not only depends on both the net angular moment and pump-laser fluence but is also dominated by the K z .