Thickness dependence of interfacial Dzyaloshinskii-Moriya interaction, magnetic anisotropy and spin waves damping in Pt/Co/Ir and Ir/Co/Pt trilayers

Asymmetric Ir/Co/Pt and Pt/Co/Ir trilayers with a wedged Co layer (Co thickness d = 0 divided by 3.6 nm) were deposited by magnetron sputtering on naturally oxidized Si substrates with a Ta/Au buffer. Their magnetic properties have been investigated using magneto-optical polar Kerr effect and Brillouin light scattering (BLS) technique in the Damon-Eshbach geometry. The BLS measurements shows a frequency asymmetry between Stokes and anti-Stokes peaks position, exploited to determine interfacial Dzyaloshinskii-Moriya interaction energy density DS. DS was nearly two times larger for the Ir/Co/Pt trilayer than for the Pt/Co/Ir with opposite chirality. The effective uniaxial magnetic anisotropy and Ds depend non-monotonically on d with a maximum at d approximate to 1.2 nm. The asymmetry in linewidth for Stokes and anti-Stokes peaks is observed for both Ir/Co/Pt and Pt/ Co/Ir trilayers for d < 1.6 nm, and it is increasing with decrease of Co thickness.