Visible to the public Unexpected Development of Perpendicular Magnetic Anisotropy in Ni/NiO Multilayers After Mild Thermal Annealing

TitleUnexpected Development of Perpendicular Magnetic Anisotropy in Ni/NiO Multilayers After Mild Thermal Annealing
Publication TypeJournal Article
Year of Publication2019
AuthorsAnyfantis, D. I., Sarigiannidou, E., Rapenne, L., Stamatelatos, A., Ntemogiannis, D., Kapaklis, V., Poulopoulos, P.
JournalIEEE Magnetics Letters
KeywordsAnisotropic magnetoresistance, anisotropy enhancement, annealing, compositionality, cyber physical systems, hysteresis loops, in-plane remanence, initially amorphous nickel oxide layers, inplane anisotropy, Internet of Things, layer roughening, Magnetic domains, Magnetic films, magnetic hysteresis, magnetic measurements, Magnetic multilayers, Magnetic Remanence, magnetic thin films, Magnetometers, mild thermal annealing, nanomagnetics, nanostructured materials, Ni-NiO, Nickel, nickel compounds, nickel layer thickness, nickel-nickel oxide multilayers, Nonhomogeneous media, normal-to-film-plane direction, partial crystallization, Perpendicular magnetic anisotropy, perpendicular magnetic recording, pubcrawl, remanence, Resiliency, size 7.0 nm, spin electronics, surface anisotropy, temperature 250.0 degC, transmission electron microscopy, volume anisotropy
AbstractWe report on the significant enhancement of perpendicular magnetic anisotropy of Ni/NiO multilayers after mild annealing up to 90 min at 250 °C. Transmission electron microscopy shows that after annealing, a partial crystallization of the initially amorphous NiO layers occurs. This turns out to be the source of the anisotropy enhancement. Magnetic measurements reveal that even multilayers with Ni layers as thick as 7 nm, which in the as-deposited state showed inplane anisotropy with square hysteresis loops, show reduced in-plane remanence after thermal treatment. Hysteresis loops recorded with the field in the normal-to-film-plane direction provide evidence for perpendicular magnetic anisotropy with up and down magnetic domains at remanence. A plot of effective uniaxial magnetic anisotropy constant times individual Ni layer thickness as a function of individual Ni layer thickness shows a large change in the slope of the data attributed to a drastic change of volume anisotropy. Surface anisotropy showed a small decrease because of some layer roughening introduced by annealing.
Citation Keyanyfantis_unexpected_2019