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

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 nonmagnetic 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 spintorque oscillator (STO) networks, or conductive channels for current-confined-path based current perpendicular-to-plane giant magnetoresistance read-heads.

Highly Tunable Magnetic and Magnetotransport Properties of Exchange Coupled Ferromagnet/Antiferromagnet-Based Heterostructures

“…Reactive RF sputtering was used to deposit the CoO layer, with O 2 as the reactive gas. By systematically varying the O 2 flow with respect to the Ar gas flow in the chamber during the deposition, we were able to tune the oxidation states of Co, starting from mixed phases of metallic Co-CoO, CoO to Co 3 O 4 (see XPS data in the Supporting Information of ref ). We strictly focus on the AFM CoO phase, mainly due to the high T N …”

Enhancement of Exchange Bias and Perpendicular Magnetic Anisotropy in CoO/Co Multilayer Thin Films by Tuning the Alumina Template Nanohole Size

“…In view of their peculiar properties, magnetic materials unveiling strong EB behavior have gained much interest owing to their widespread applications in sensors [ 14 ], spintronic devices [ 15 , 16 ], drug carriers [ 17 ], and magnetic read heads for magnetic information storage devices [ 18 ]. In addition, AFM/FM multilayer (ML) thin films with strong perpendicular magnetic anisotropy (PMA) have become a key factor in improving magnetic logic chips, spintronic devices, and random-access memory devices [ 19 , 20 , 21 ].…”

The large perpendicular magnetic anisotropy induced at the Co2FeAl/MgAl2O4 interface and tuned with the strain, voltage and charge doping by first principles study

“…Magnetic tunnel junctions (MTJs) with induced perpendicular magnetic anisotropy (PMA) at the interface have attracted great attention [1][2][3][4][5][6] due to their potential applications in spintronic devices towards faster and more small magnetic bits, such as non-volatile magnetic random-access memory (MRAM) [7][8][9][10][11]. Compared with in-plane magnetic anisotropy (IMA) MTJs, perpendicular anisotropy MTJ (p-MTJ) cells are beneficial to maintain high thermodynamic stability and reduce the working energy consumption of MRAMs as they have a lower critical switching current density [12].…”