Improving the Magnetic Properties of Co–CoO Systems by Designed Oxygen Implantation Profiles

Abstract

Oxygen implantation in ferromagnetic Co thin films is shown to be an advantageous route to improving the magnetic properties of Co−CoO systems by forming multiple nanoscaled ferromagnetic/antiferromagnetic interfaces homogeneously distributed throughout the layer. By properly designing the implantation conditions (energy and fluence) and the structure of the films (capping, buffer, and Co layer thickness), relatively uniform O profiles across the Co layer can be achieved using a single-energy ion implantation approach. This optimized configuration results in enhanced exchange bias loop shifts, improved loop homogeneity, increased blocking temperature, reduced relative training effects and increased retained remanence in the trained state with respect to both Co/CoO bilayers and Oimplanted Co films with a Gaussian-like O depth profile. This underlines the great potential of ion implantation to tailor the magnetic properties by controllably modifying the local microstructure through tailored implantation profiles.

Rotatable anisotropy driven training effects in exchange biased Co/CoO films

“…Moreover, the blocking temperature of the samples of Gruyters is around 175 K, whereas the blocking temperature of our CoO layer is 125 K, suggesting that the formed CoO might be more hyperstoichiometric with a higher degree of polycrystallinity, i.e., more prone to nanostructuring effects. 22,37 The best fitting magnetization curves, simulated through the above model, are also plotted in Fig. 1.…”

Lateral Magnetically Modulated Multilayers by Combining Ion Implantation and Lithography

“…The O incorporation into the Co layer (reaching around 29 at% of O at a half depth of the Co layer, Figure a) occurs mainly via a grain boundary oxidation mechanism, as confirmed by the evolution of crystallite size with O ion implantation in similar Co thin films . With ion implantation, the Co grain boundaries oxidize, leading to the growth of the CoO counterpart (58 at%) . Note that increasing the fluence would eventually lead to pure antiferromagnetic CoO patterned lines, which could probably result in effects like lateral exchange bias …”

“…Furthermore, irradiation using heavy ions and ion implantation have also been utilized with the aim to induce increased collisional damage and/or to create composition adjustments . Recently, oxygen ion implantation has been confirmed as an advantageous route to form antiferromagnetic (AFM) oxides embedded in FM thin films (e.g., Co), giving rise to exchange bias . In parallel, the wide variety of lithography techniques yields a high flexibility in pattern design and, thus, in shadow mask fabrication for ion implantation.…”

Unraveling the Origin of Magnetism in Mesoporous Cu-Doped SnO2 Magnetic Semiconductors

“…Namely, the XMCD signal at +50 kOe is significantly larger than at −50 kOe ( Table 2 ), confirming spin frustration upon reversal due to size effects. This is more pronounced in the sample with higher Cu content, suggesting that, at higher doping concentrations, a more stoichiometric CuO phase with a better defined magnetic anisotropy is formed [ 65 ].…”