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標題: Annealing effect of NiO/Co90Fe10 thin films: From bilayer to nanocomposite
作者: Xu Li
Yu-Chi Chang
Jiann-Yeu Chen
Ko-Wei Lin
Ryan D. Desautels
Johan van Lierop
Philip W.T. Pong
關鍵字: Exchange bias;Magnetic thin film;Nanocomposite
Project: Physics Letters A, Volume 382, Issue 39, 5 October 2018, Pages 2886-2893
Exchange-biased bilayers are widely used in the pinned layers of spintronic devices. While magnetic field annealing (MFA) was routinely engaged during the fabrication of these devices, the annealing effect of NiO/CoFe bilayers is not yet reported. In this paper, the transition from NiO/Co90Fe10 bilayer to nanocomposite single layer was observed through rapid thermal annealing at different temperatures under magnetic field. The as-deposited and low-temperature (<623 K) annealed samples had rock salt (NiO) and face center cubic (Co90Fe10) structures. On the other hand, annealing at 623 K and 673 K resulted in nanocomposite single layers composed of oxides (matrix) and alloys (precipitate), due to grain boundary oxidization and strong interdiffusion in the NiO/CoFe and CoFe/SiO2 interfaces. The structural transition was accompanied by the reduction of grain sizes, re-ordering of crystallites, incensement of roughness, and reduction of Ni2+. When measured at room temperature, the bilayers exhibited soft magnetism with small room-temperature coercivity. The nanocomposite layers exhibited an enhanced coercivity due to the changes in the magnetization reversal mechanism by pinning from the oxides. At 10 K, the increased antiferromagnetic anisotropy in the NiO resulted in enhanced coercivity and exchange bias in the bilayers. The nanocomposites exhibited weaker exchange bias compared with the bilayers due to frustrated interfacial spins. This investigation on how the magnetic properties of exchange-biased bilayers are influenced by magnetic RTA provides insights into controlling the magnetization reversal properties of thin films.
DOI: 10.1016/j.physleta.2018.07.018
Appears in Collections:材料科學與工程學系

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