Pd as a promoter to reduce Co cluster films at room temperature

Romero, C.P.; Avila, J. I.; Trabol, R.; Wang, Huan; Vantomme, André; Bael, M. J. Van; Lievens, Peter; Cabrera, A. L.

doi:10.1016/j.ijhydene.2010.01.026

Cited by 11 publications

(3 citation statements)

References 23 publications

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“…17,18 This indicates H 2 adsorption does not affect the magnetization processes of magnetic films, and the MO enhancement should originate from H 2 -induced change of Pd optical properties. 10,17,18,[23][24][25] On the other hand, the post-annealed Pd/Co/Pd preferred an oblique magnetic easy axis. Magnetic hysteresis loops of comparable H C were observable in both perpendicular and inplane MOKE geometry.…”

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confidence: 99%

Hydrogenation induced reversible modulation of perpendicular magnetic coercivity in Pd/Co/Pd films

Lin¹,

Tsai

Wang

et al. 2013

Applied Physics Letters

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In perpendicularly magnetized Pd/Co/Pd trilayers, the hydrogenation not only increased Kerr signal but also significantly enhanced the magnetic coercivity (HC) by 17%. The reversibility was demonstrated by cyclic H2 exposure. The time constants of hydrogen absorption and desorption effect on HC range from tens to hundreds seconds, depending on the H2 gas pressure. The magneto-optical Kerr signal and magnetic coercivity was simultaneously recorded during H2 absorption and desorption. These multifarious signals respond differently and provide a detailed understanding of hydrogenation effect on the functional Pd/Co/Pd trilayers.

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confidence: 99%

Hydrogenation induced reversible modulation of perpendicular magnetic coercivity in Pd/Co/Pd films

Lin¹,

Tsai

Wang

et al. 2013

Applied Physics Letters

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“…The reactivity of metal clusters and nanoparticles with small molecules may be controlled through their electronic structure. − The quantum confinement of electrons by the spherical potential in spherical clusters leads to the bunching of electronic levels into shells which exhibit a uniform surface distribution of charge. On the other hand, metal clusters with distorted geometries can have uneven charge distributions that may promote complementary active sites that can activate polar covalent bonds. − Herein, we present experimental and theoretical findings which reveal that the strong CO carbonyl bond of formaldehyde can be split by complementary active sites on size-selective aluminum cluster anions.…”

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confidence: 99%

Carbonyl Bond Cleavage by Complementary Active Sites

et al. 2013

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We have studied the size-selective reactivity of Al n − clusters with formaldehyde to determine if carbonyl bonds may be broken by complementary active sites. Gas phase experiments reveal that Al n − , where n = 8−12, react with formaldehyde to form Al n−2 CH 2 − , which demonstrates that the carbonyl bond is broken in the reaction with the cluster, while Al 13 − is found to be resistant to reaction. The most likely leaving group is determined to be Al 2 O. We also found n = 15−19 to be reactive with the products being a mix of Al n−2 CH 2 − and Al n (OCH 2 ) m − . Theoretical investigations find that the adjacent Lewis acid and Lewis base sites stabilize the resonance structure in which the carbonyl is reduced to a single bond which encourages carbonyl cleavage. A transition state analysis of the cleavage of the carbonyl bond confirms the size selective cleavage of the carbonyl bond and supports the importance of complementary Lewis acid−Lewis base active sites in governing the reactivity.

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“…Although the exposure to ambient certainly results in an exposure to oxygen, it cannot be ruled out that traces of oxygen were already present on the substrate and this oxygen migrated from the substrate into the cluster assembled films. In some cases the oxygen need to be reduced in a mild atmosphere of H 2 [14]. Two samples (A and B) were produced on polished (0001) oriented sapphire and capped with 3.5 nm of Pd using a commercial e-beam evaporator loaded with a pure Pd rod (purity 99.99%).…”

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Passivation of cobalt nanocluster assembled thin films with hydrogen

et al. 2012

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The effect of hydrogen passivation on bare and Pd capped cobalt nanocluster assembled thin films was studied with Rutherford backscattering spectrometry (RBS) and magnetic force microscopy (MFM) after exposure to ambient conditions. The nanoclusters are produced in a laser vaporization cluster source in which the helium carrier gas was mixed with hydrogen. RBS revealed that oxidation of the Co nanoclusters is considerably reduced by the presence of hydrogen during cluster formation. The capping did not modify the influence of the passivation. The hydrogen passivation method is especially effective in cases when capping of the films is not desirable, for example for magnetic studies. Clear differences in the magnetic domain structures between hydrogen passivated and non-passivated Co nanocluster films were demonstrated by MFM and are attributed to a difference in inter-cluster magnetic interaction, which is critically depending on the CoO content. The hydrogen passivation method may be used to tailor and stabilize properties of nanocluster assembled thin films.

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Pd as a promoter to reduce Co cluster films at room temperature

Cited by 11 publications

References 23 publications

Hydrogenation induced reversible modulation of perpendicular magnetic coercivity in Pd/Co/Pd films

Hydrogenation induced reversible modulation of perpendicular magnetic coercivity in Pd/Co/Pd films

Carbonyl Bond Cleavage by Complementary Active Sites

Passivation of cobalt nanocluster assembled thin films with hydrogen

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