Ga⁺ ion irradiation-induced changes in magnetic anisotropy of a Pt/Co/Pt thin film studied by X-ray magnetic circular dichroism

¹ Photon Factory & Condensed Matter Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 305-0801 Tsukuba, Japan
² Department of Physics, University of Bialystok, 15-424 Białystok,  Poland
³ Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
⁴ Institute of Physics, Polish Academy of Sciences, 02-668 Warszawa, Poland

Abstract

Ga⁺ ion irradiation-induced changes in magnetic anisotropy of a Pt/Co/Pt ultrathin film are investigated by means of the X-ray magnetic circular dichroism (XMCD) technique. A large difference in the Co orbital moment is observed between out-of-plane and in-plane directions of the film at moderate Ga⁺ fluences of ~1-2×10¹⁴ ions/cm², which corresponds to the perpendicular magnetic anisotropy (PMA), while further increased fluences reduce the orbital moment difference, resulting in in-plane magnetization. In contrast, at much higher Ga⁺ fluences of ~5×10¹⁵ ions/cm², at which PMA is observed again, no significant difference is found in the orbital moment of Co between out-of-plane and in-plane directions. Different origins are thus suggested for the appearance of PMA induced by the irradiation between moderate and high Ga⁺ fluences.