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Materials 2017, 10(7), 717; doi:10.3390/ma10070717

Magnetic Hysteresis in Nanocomposite Films Consisting of a Ferromagnetic AuCo Alloy and Ultrafine Co Particles

1
Dipartimento di Fisica e Scienze della Terra and CNISM, Università di Ferrara, I-44122 Ferrara, Italy
2
Dipartimento di Fisica e Astronomia and CNISM, Università di Padova, I-35131 Padova, Italy
*
Author to whom correspondence should be addressed.
Received: 14 June 2017 / Revised: 22 June 2017 / Accepted: 26 June 2017 / Published: 28 June 2017
(This article belongs to the Special Issue Advances in Superconductive and Magnetic Nanomaterials)
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Abstract

One fundamental requirement in the search for novel magnetic materials is the possibility of predicting and controlling their magnetic anisotropy and hence the overall hysteretic behavior. We have studied the magnetism of Au:Co films (~30 nm thick) with concentration ratios of 2:1, 1:1, and 1:2, grown by magnetron sputtering co-deposition on natively oxidized Si substrates. They consist of a AuCo ferromagnetic alloy in which segregated ultrafine Co particles are dispersed (the fractions of Co in the AuCo alloy and of segregated Co increase with decreasing the Au:Co ratio). We have observed an unexpected hysteretic behavior characterized by in-plane anisotropy and crossed branches in the loops measured along the hard magnetization direction. To elucidate this phenomenon, micromagnetic calculations have been performed for a simplified system composed of two exchange-coupled phases: a AuCo matrix surrounding a Co cluster, which represents an aggregate of particles. The hysteretic features are qualitatively well reproduced provided that the two phases have almost orthogonal anisotropy axes. This requirement can be plausibly fulfilled assuming a dominant magnetoelastic character of the anisotropy in both phases. The achieved conclusions expand the fundamental knowledge on nanocomposite magnetic materials, offering general guidelines for tuning the hysteretic properties of future engineered systems. View Full-Text
Keywords: magnetic hysteresis; magnetic anisotropy; exchange interaction; nanocomposite material; SQUID magnetization measurements; micromagnetic modeling magnetic hysteresis; magnetic anisotropy; exchange interaction; nanocomposite material; SQUID magnetization measurements; micromagnetic modeling
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Chinni, F.; Spizzo, F.; Montoncello, F.; Mattarello, V.; Maurizio, C.; Mattei, G.; Bianco, L.D. Magnetic Hysteresis in Nanocomposite Films Consisting of a Ferromagnetic AuCo Alloy and Ultrafine Co Particles. Materials 2017, 10, 717.

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