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

• A new kind of perpendicular thin film material, oxidized CoFeAl, has been fabricated.
• The precession frequency and effective damping are strongly affected by higher fluence.
• The effective damping factor increases with oxygen partial pressure.
• The intrinsic damping factor is below 0.028 for the CFAO film with Ku=4.3×106 erg/cm3.

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 Fp can affect the effective magnetic anisotropy field and thus the precession frequency f seriously, leading to an increased dependence of effective magnetic damping factor αeff on the external field at higher fluences. Moreover, the αeff increases with increasing the oxygen partial pressure PO2 while the uniaxial anisotropy energy Ku and Landau factor g decrease, owing to the increased proportion of superparamagnetic CoFe oxides formed by over-oxidation. By optimizing both the Fp and PO2, 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.