Influence of Ar-assisted pulsed laser ablation on structural and magnetic properties of Fe₈0B20 thin films

We report on the chemical, structural and morphological modifications introduced in nanothick Fe₈₀B₂₀ films by the use of Ar assistance (at different pressures) during their pulsed laser ablation deposition process. As a reference, a film deposited in absence of Ar and under ultra-high vacuum conditions was also prepared. Samples were characterized from the measurement of X-ray photoelectron spectroscopy depth profiles, atomic force microscopy, and transmission electron microscopy as well as from the standpoint of their dc angular dependence of the hysteresis, high applied field magnetization and tens of GHz dynamics. Our results include i) the induction of surface roughening that increases with the assisting gas pressure, ii) the amorphousness of the ultra-high vacuum film, iii) the induction, by the Ar assistance, of partial crystallization, yielding Fe-rich columns whose transverse dimension increased with the Ar pressure, iv) the progressive isotropization of the in-plane hysteresis parameters associated to the increase of Ar pressure, v) the occurrence on the samples deposited with the largest Ar pressures of spin waves stiffness constant having a magnitude 20 times larger than the value measured in the reference sample, and vi) the decrease of the ferromagnetic resonance damping parameter with regard to the reference sample.