Monton, C., F. de la Cruz, and J. Guimpel. "Magnetic behavior of superconductor/ferromagnet superlattices." PHYSICAL REVIEW B 75, no. 6 (2007).
Abstract: A study of the electromagnetic response of superconductor/ferromagnet Nb/Co superlattices is presented. The dc magnetization is measured as a function of Co layer thickness, applied field H-a, and temperature. For very thin Co layers, no ferromagnetism is detected and the observed response is essentially that of a collection of uncoupled Nb layers. When the Co layer is thick enough for ferromagnetism to be established, prior to the field-cooled magnetization measurements, the Co layers are magnetically saturated in the parallel or antiparallel directions to H-a. In this case, the magnetic response of the otherwise uncoupled Nb layers is found to depend on both H-a and the stray fields.
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Monton, C., F. de la Cruz, and J. Guimpel. "Magnetic state modification induced by superconducting response in ferromagnet/superconductor Nb/Co superlattices." PHYSICAL REVIEW B 77, no. 10 (2008).
Abstract: Magnetization measurements in superconductor/ferromagnet Nb/Co superlattices show a complex behavior as a function of temperature, applied field, and sample history. Based on a simple model, it is shown that this behavior is due to an interplay between the superconductor magnetization temperature dependence, the ferromagnet magnetization time dependence, and the stray fields of both materials. It is also shown that the magnetic state of the Co layers is modified by the Nb superconducting response, implying that the problem of a superconductor/ferromagnetic heterogeneous sample has to be solved in a self-consistent manner.
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Monton, C., C. A. Ramos, J. Guimpel, and R. D. Zysler. "Experimental evidence of magnetic anisotropy induction by superconductivity in superlattices." Applied Physics Letters 92, no. 15 (2008).
Abstract: We present a study of Nb/Co superlattices by ferromagnetic resonance. We find that when the superconductor enters the Meissner state, an anisotropy field around 400 Oe, parallel to the applied field, appears in the ferromagnetic layers, consistent with the superconducting flux expelled from the superconducting layers. This anisotropy field is an important key to understand previous results showing that the superconductor layers modify the magnetic state of the ferromagnetic layers. (c) 2008 American Institute of Physics.
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Guimpel, J., C. Monton, N. Haberkorn, and F. de la Cruz. "Magnetic behaviour of superconductor/ferromagnet metallic and perovskite based superlattices." physica status solidi (c) 4, no. 11 (2007): 4174–4180.
Abstract: We present a study of the magnetic behaviour of superconducting/ferromagnetic superlattices, both for metallic and perovskite based systems. In the first case we find that the response is determined by the ferromagnetic layer regime. If these layers are very thin, no ferromagnetism is observed, but the superconducting layers are decoupled, and the superlattice behaves as a stack of independent superconducting films. For thicker ferromagnetic films, ferromagnetism is established and the effective field resulting from the superposition of stray and applied fields dominates the superconducting response of the superlattice. For the perovskite based superlattices, the physical properties are more affected by interface disorder. In this case we have found that the behaviour can be interpeted as charge carrier transfer between both materials, inducing a change in the magnetic character of the manganite. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Monton, C., J. Guimpel, and F. de la Cruz. "Superconducting behaviour of Nb/Co superlattices." Applied Surface Science 254, no. 1 (2007): 375–377.
Abstract: We study the superconducting and magnetic behaviour of Nb/Co superlattices, for superconducting Nb layer thickness of 44 nm and Co layer thickness less than 1 nm. In this limit no ferromagnetism is observed for Co. The superlattice behaves as independent superconducting Nb layers. We obtain the penetration depth and superconducting gap of the material, and analyze the results in terms of microscopic models and theories. (C) 2007 Elsevier B.V. All rights reserved.
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