Laser heating and oxygen partial pressure effects on the dynamic magnetic properties of perpendicular CoFeAlO films

The impact of oxidation and laser heating on the dynamic magnetic properties of perpendicularly magnetized Co₅₀Fe₂₅Al₂₅O films has been studied by time-resolved magneto-optical Kerr effect in a fs-laser pump-probe setup. We find that pump laser fluence F_p can affect the effective magnetic anisotropy field and thus the precession frequency f seriously, leading to an increased dependence of effective magnetic damping factor α_eff on the external field at higher fluences. Moreover, the α_eff increases with increasing the oxygen partial pressure P_O2 while the uniaxial anisotropy energy K_u and Landau factor g decrease, owing to the increased proportion of superparamagnetic CoFe oxides formed by over-oxidation. By optimizing both the F_p and P_O2, the intrinsic damping factor is determined to be lower than 0.028 for the perpendicular film showing a uniaxial anisotropy energy as high as 4.3×10⁶ erg/cm³. The results in this study provide a promising approach to manipulate the magnetic parameters for possible applications in spintronic devices.