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Anyfantis, D. I., Sarigiannidou, E., Rapenne, L., Stamatelatos, A., Ntemogiannis, D., Kapaklis, V., Poulopoulos, P..  2019.  Unexpected Development of Perpendicular Magnetic Anisotropy in Ni/NiO Multilayers After Mild Thermal Annealing. IEEE Magnetics Letters. 10:1–5.
We 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.
Codescu, M. M., Kappel, W., Chitanu, E., Manta, E..  2017.  Exchange hardened ferrimagnetic nanocomposites. 2017 10th International Symposium on Advanced Topics in Electrical Engineering (ATEE). :444–447.

Having significant role in the storing, delivering and conversion of the energy, the permanent magnets are key elements in the actual technology. In many applications, the gap between ferrites and rare earths (RE) based sintered permanent magnets is nowadays filled by RE bonded magnets, used in more applications, below their magnetic performances. Therewith, the recent trends in the RE market concerning their scarcity, impose EU to consider alternative magnets (without RE) to fill such gap. The paper presents the chemical synthesis of the exchange coupled SrFe12O19/CoFe2O4 nanocomposites, based on nanoferrites. The appropriate annealing leads to the increasing of the main magnetic characteristics, saturation magnetization MS and intrinsic coercivity Hc, in the range of 49 - 53 emu/g, respectively 126.5 - 306 kA/m. The value reached for the ratio between remanent magnetization and saturation magnetization is higher than 0.5, fact that proved that between the two magnetic phases occurred exchange interaction.