Publications by authors named "Juan P Andres"

The interest in magnetic nanostructures exhibiting perpendicular magnetic anisotropy and exchange bias (EB) effect has increased in recent years owing to their applications in a new generation of spintronic devices that combine several functionalities. We present a nanofabrication process used to induce a significant out-of-plane component of the magnetic easy axis and EB. In this study, 30 nm thick CoO/Co multilayers were deposited on nanostructured alumina templates with a broad range of pore diameters, 34 nm ≤ Dp ≤ 96 nm, maintaining the hexagonal lattice parameter at 107 nm.

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Ferrimagnetic thin films formerly played a very important role in the development of information storage technology. Now they are again at the forefront of the rising field of spintronics. From new, more efficient magnetic recording media and sensors based on spin valves to the promising technologies envisaged by all-optical switching, ferrimagnets offer singular properties that deserve to be studies both from the point of view of fundamental physics and for applications.

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We present a detailed study about the substrate-induced strain and thickness effects on the structure and magnetic properties of LaSrCoO films. The in-plane tensile or compressive strain imposed by four different substrates configures an in-plane or out-of-plane easy axis, respectively. The presence of a soft magnetic phase at the interface is also conditioned by the type of strain.

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We report on the growth of MnGethin films on Ge(001) substrates following two methods: solid phase epitaxy (SPE) and reactive deposition epitaxy (RDE). We have varied the thickness of the films, in order to study the magnetization and anisotropy evolution. A strongly enhanced magnetization of 1580 kA m, compared to 1200 ± 150 kA mfor films grown on Ge(111), has been measured on ultrathin films of 5 nm grown by RDE.

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CuCo thin films have been obtained by sputtering (x = 3, 9) and sputter gas aggregation (x = 2.5, 7.5) and subsequent annealing at 400 °C for 1 h.

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The influence of the thickness of the NiFe (Permalloy, Py) layers on the structural and magnetic properties of magnetron sputtered Py/Ti multilayers was studied. The thickness of the Py layers was varied in the interval of 8 to 30 Å. X-ray reflectivity scans evidence the existence of a well-defined layered structure in all the samples considered, but also the presence of a complex intermixed interface.

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Article Synopsis
  • Porous films containing cobalt nanoparticles were created through a method called sputter gas aggregation and were oxidized in air at 100 °C for various durations, which affected their magnetic properties, particularly the exchange bias field.* -
  • Air annealing was found to be an effective technique to fine-tune the Co/CoO ratio, leading to an optimal exchange bias field exceeding 6 kOe at low temperatures (5 K).* -
  • Changes in the magnetization loops, including vertical shifts and a unique "hummingbird-like" shape, were linked to the density of uncompensated spins and the oxidation process, though the exact cause of the soft magnetic phase remains unclear.*
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