Modifications of magnetic properties of Pt/Co/Pt thin layers by focused gallium ion beam irradiation

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Vieu, C. | Gierak, J. | Launois, H. | Aign, T. | Meyer, P. | Jamet, J.P. | Ferré, J. | Chappert, C. | Devolder, T. | Mathet, V. | Bernas, H.

Edité par CCSD ; American Institute of Physics -

International audience. We show how the magnetic properties of the Pt/Co ultrathin film structure can be modified and even controlled under uniform irradiation by Ga+ ions at low fluence in the 20-100 keV range. A systematic magneto-optical study is presented for the Pt/Co(1.4 nm)/Pt(111) ultrathin-film structure. At ion fluences below D=1014Ga+/cm2, the coercive field is steadily reduced when increasing the fluence. At large fluences, in the range D=(5-10)×1014Ga+ions/cm2, the magnetization of the Co layer drops rapidly and the film finally becomes paramagnetic at room temperature for D>2×1015Ga+ions/cm2. We demonstrate that these magnetic changes are related to the effect of ion-induced collisional intermixing of the Co/Pt interfaces, leading to the formation of stable Co-Pt alloys with varying composition across the interfaces. A simple model is derived to relate the ion beam-induced mixing to the changes in magnetic properties. The present work allows us to gain a quantitative understanding of previous experiments using a focused Ga+ ion beam to pattern magnetic properties of similar samples at a sub-100 nm scale.

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