Tailoring magnetic properties of Co nanocluster assembled films using hydrogen

•Low amounts of hydrogen exposure during fabrication changes magnetic properties.•This is an easy method to tailor the magnetic properties of cluster assembled thin films.•Significant magnetic changes are shown. Tailoring magnetic properties in nanocluster assembled cobalt (Co) thin films was achiev...

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Bibliographic Details
Published in:Journal of magnetism and magnetic materials 2018-07, Vol.458, p.261-267
Main Authors: Romero, C.P., Volodin, A., Paddubrouskaya, H., Van Bael, M.J., Van Haesendonck, C., Lievens, P.
Format: Article
Language:English
Subjects:
Antiferromagnetism
Bias
Clusters
Coercivity
Crystal structure
Ferromagnetic materials
Hydrogen
Hydrogen storage
Magnetic fields
Magnetic measurement
Magnetic properties
Magnetism
Nanoclusters
Nanostructured materials
Oxidation
Oxygen content
Thin films
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Summary:•Low amounts of hydrogen exposure during fabrication changes magnetic properties.•This is an easy method to tailor the magnetic properties of cluster assembled thin films.•Significant magnetic changes are shown. Tailoring magnetic properties in nanocluster assembled cobalt (Co) thin films was achieved by admitting a small percentage of H2 gas (∼2%) into the Co gas phase cluster formation chamber prior to deposition. The oxygen content in the films is considerably reduced by the presence of hydrogen during the cluster formation, leading to enhanced magnetic interactions between clusters. Two sets of Co samples were fabricated, one without hydrogen gas and one with hydrogen gas. Magnetic properties of the non-hydrogenated and the hydrogen-treated Co nanocluster assembled films are comparatively studied using magnetic force microscopy and vibrating sample magnetometry. When comparing the two sets of samples the considerably larger coercive field of the H2-treated Co nanocluster film and the extended micrometer-sized magnetic domain structure confirm the enhancement of magnetic interactions between clusters. The thickness of the antiferromagnetic CoO layer is controlled with this procedure and modifies the exchange bias effect in these films. The exchange bias shift is lower for the H2-treated Co nanocluster film, which indicates that a thinner antiferromagnetic CoO reduces the coupling with the ferromagnetic Co. The hydrogen-treatment method can be used to tailor the oxidation levels thus controlling the magnetic properties of ferromagnetic cluster-assembled films.
ISSN:0304-8853
1873-4766
DOI:10.1016/j.jmmm.2018.03.038