On defects' role in enhanced perpendicular magnetic anisotropy in Pt/Co/Pt, induced by ion irradiation.

Modifications of magnetic and magneto-optical properties of Pt/Co(d _Co )/Pt upon Ar ⁺ irradiation (with energy 1.2, 5 and 30 keV) and fluence, F at the range from 2 · 10 ¹³ -2 · 10 ¹⁶ Ar ⁺ cm ^-2 ) were studied. Two 'branches' of increased perpendicular magnetic anisotropy (PMA) and enhanced magneto-optical response are found on 2D (d _Co , F) diagrams. The difference in F between 'branches' is driven by ion energy. Structural features correlated with magnetic properties have been analysed thoroughly by x-ray diffraction, Rutherford backscattering spectrometry and positron annihilation spectroscopy. Experimental results are in agreement with TRIDYN numerical calculations of irradiation-induced layers intermixing. Our work discusses particularly structural factors related to crystal lattice defects and strain, created and modified by irradiation, co-responsible for the increase in the PMA.