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arXiv · 2002.08090

Ion-Irradiation-Induced Cobalt/Cobalt Oxide Heterostructures: Printing 3D Interfaces

Oğuz Yıldırım·Donovan Hilliard·Sri Sai Phani Kanth Arekapudi·Ciarán Fowley·Hamza Cansever·Leopold Koch·Lakshmi Ramasubramanian·Shengqiang Zhou·Roman Böttger·Jürgen Lindner·Jürgen Faßbender·Olav Hellwig·Alina M. Deac
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Abstract

Interfaces separating ferromagnetic (FM) layers from non-ferromagnetic layers offer unique properties due to spin-orbit coupling and symmetry breaking, yielding effects such as exchange bias, perpendicular magnetic anisotropy, spin-pumping, spin-transfer torques, conversion between charge and spin currents and vice-versa. These interfacial phenomena play crucial roles for magnetic data storage and transfer applications, which require forming FM nano-structures embedded in non-ferromagnetic matrices. Here, we investigate the possiblity of creating such nano-structures by ion-irradiation. We study the effect of lateral confinement on the ion-irradiation-induced reduction of non-magnetic metal oxides (e.g., antiferro- or paramagnetic) to form ferromagnetic metals. Our findings are later exploited to form 3-dimensional magnetic interfaces between Co, CoO and Pt by spatially-selective irradiation of CoO/Pt multilayers. We demonstrate that the mechanical displacement of the O atoms plays a crucial role during the reduction from insulating, non-ferromagnetic cobalt oxides to metallic cobalt. Metallic cobalt yields both perpendicular magnetic anisotropy in the generated Co/Pt nano-structures, and, at low temperatures, exchange bias at vertical interfaces between Co and CoO. If pushed to the limit of ion-irradiation technology, this approach could, in principle, enable the creation of densely-packed, atomic scale ferromagnetic point-contact spin-torque oscillator (STO) networks, or conductive channels for current-confined-path based current perpendicular-to-plane giant magnetoresistance read-heads.

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Oğuz Yıldırım, Donovan Hilliard, Sri Sai Phani Kanth Arekapudi, Ciarán Fowley, Hamza Cansever, Leopold Koch, Lakshmi Ramasubramanian, Shengqiang Zhou, Roman Böttger, Jürgen Lindner, Jürgen Faßbender, Olav Hellwig, Alina M. Deac. 2020-02-19. Ion-Irradiation-Induced Cobalt/Cobalt Oxide Heterostructures: Printing 3D Interfaces. https://doi.org/10.1021/acsami.9b13503

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