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Structure and magnetism in Cr-embedded Co nanoparticles

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journal contribution
posted on 18.12.2015, 12:10 by Stephen Henry Baker, M. S. Kurt, M. Roy, M. R. Lees, C. Binns
We present the results of an investigation into the atomic structure and magnetism of 2 nm diameter Co nanoparticles embedded in an antiferromagnetic Cr matrix. The nanocomposite films used in this study were prepared by co-deposition directly from the gas phase, using a gas aggregation source for the Co nanoparticles and a molecular beam epitaxy (MBE) source for the Cr matrix material. Co K and Cr K edge extended x-ray absorption fine structure (EXAFS) experiments were performed in order to investigate atomic structure in the embedded nanoparticles and matrix respectively, while magnetism was investigated by means of a vibrating sample magnetometer. The atomic structure type of the Co nanoparticles is the same as that of the Cr matrix (bcc) although with a degree of disorder. The net Co moment per atom in the Co/Cr nanocomposite films is significantly reduced from the value for bulk Co, and decreases as the proportion of Co nanoparticles in the film is decreased; for the sample with the most dilute concentration of Co nanoparticles (4.9% by volume), the net Co moment was 0.25 μ B/atom. After field cooling to below 30 K all samples showed an exchange bias, which was largest for the most dilute sample. Both the structural and magnetic results point towards a degree of alloying at the nanoparticle/matrix interface, leading to a core/shell structure in the embedded nanoparticles consisting of an antiferromagnetic CoCr alloy shell surrounding a reduced ferromagnetic Co core.

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Citation

Journal of Physics : Condensed Matter, 2016, 28(4), 046003

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

AM (Accepted Manuscript)

Published in

Journal of Physics : Condensed Matter

issn

0953-8984

eissn

1361-648X

Acceptance date

11/12/2015

Copyright date

2016

Available date

07/01/2017

Publisher version

http://iopscience.iop.org/article/10.1088/0953-8984/28/4/046003/meta

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The file associated with this record is under a 12-month embargo from publication in accordance with the publisher's self-archiving policy, available at http://authors.iop.org/atom/help.nsf/0/F20EC7D4A1A670AA80256F1C0053EEFF?OpenDocument. The full text may be available through the publisher links provided above.

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en

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