Dzyaloshinskii-Moriya interaction and magnetic anisotropy in Pt/Co/Au trilayers modified by Ga+ ion irradiation

Abstract The influence of 30 keV Ga+ ion irradiation in the fluence range 0 ÷ 1·1016 ions/cm2 on magnetic properties of Pt(bottom)/Co(3 nm)/Au(top) trilayers grown by the molecular beam epitaxy was studied. Polar magnetooptical Kerr effect magnetometry and Brillouin light scattering spectrometry were used to measure the magnetic anisotropy and the strength of Dzyaloshinskii-Moriya interaction (DMI). The as-deposited sample exhibits in-plane magnetization with an effective anisotropy field of −0.35 ± 0.02 T. Magnetic anisotropy gradually grows as the ion fluence is increased and out-of-plane magnetic anisotropy appears for the fluence above ∼ 3·1015 ions/cm2. The frequency asymmetry in Stokes and anti-Stokes lines Δf, being a measure of DMI strength, was determined from Brillouin light scattering investigations as a function of applied fluence. The effective DMI constant is equal to −0.48 ± 0.05 mJ/m2 in the as-deposited sample. While increasing fluence the parameter Δf: (i) varies non-monotonically (with two maxima) for F smaller than F≈1015 ions/cm2 and (ii) gradually decreases to zero for higher fluences. Our results can be used for the adjustment of DMI interaction in the manufacturing of magnonic nano-devices.