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Gómez, M. E., G. Campillo, J. - G. Ramirez, A. Hoffmann, and J. Guimpel. "Detailed magnetic and structural properties of exchange-biased La1-xCaxMnO3." physica status solidi (c) 4, no. 11 (2007): 4181–4187.
Abstract: We measured structural, magnetic and, magneto-transport properties of heterostructures consisting of La1–xCaxMnO3 ferromagnetic (FM) layers (x = 0.33) and antiferromagnetic (AF) layers (x = 0.67). We grew FM/AF superlattices via a high-pressure sputtering technique on (001) oriented SrTiO3 substrates. We systematically varied the thickness of the ferromagnetic layers, while maintaining a fixed thickness of the antiferromagnetic layers. Alternatively, we also varied the thickness of the antiferromagnetic layers, keeping a fixed ferromagnetic layer thickness. The total superlattice thickness was kept approximately constant. XRD analysis confirms the existence of the superlattice structure by the observation of multiple satellite peaks around the (00l) manganite Bragg reflections. We extracted the average lattice parameter of the superlattice and its dependence on the thicknesses of the ferro- and antiferromagnetic layers. We conducted field cooling (FC) and zero field cooling (ZFC), magneto-thermal, and magneto-resistance measurements. The existence of an exchange bias effect at temperatures below the Néel temperature of the AF layer was revealed by magnetization loops measured after FC. We studied the dependence of magnetic parameters on the thicknesses of the ferro- and antiferromagnetic layers. We found that the structural, magnetization, and magneto transport properties as functions of F-layer thickness are all correlated. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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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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