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Cuba es uno de los pocos Jugares en el mundo donde se obtiene producción industrial de petró1eo en rocas de la asociación ofiolítica. El primer yacimiento descubierto fue Motembo en 1881 y el más reciente Cantiel en el año 1978. Los afloramientos de ofiolita -en su mayoría de serpentinita- pueden medir desde pocos metros hasta varios kilómetros de extensión y están sobre corridos en dirección de sur a norte, presentado gran tectonismo y metamorfismo superpuesto. Estos yacimientos de poca profundidad presentan grandes débitos de hidrocarburo en su etapa de explotación inicial, el cual migró desde rocas sedimentarias mas profundas principalmente carbonatos. Se detectaban por la perforación de pozos cerca de las manifestaciones de hidrocarburo en la superficie o en las exploraciones hacia objetivos mas profundos, como las secuencias carbonatadas de la Unidad Tectono-Estratigrafica (UTE) Placetas y Camajuani. Se creó una hipótesis genético-dinámica de la formación del cinturón ofiolítico y sus cabalgamientos y un modelo geó1ogo-geoffsico para explicar las características de estas trampas. A partir de este modelo y sobre la base de una novedosa metodóloga de modelación matemática, se aplicó a problemas de reconocimiento de patrones en dominios poco formalizados del conocimiento, se procesó la información correspondiente a las areas en estudio y se dieron respuestas a muchas interrogantes de esta problemática. doi: https://doi.org/10.22201/igeof.00167169p.1994.33.3.1183

Equiatomic FePt in the A1 soft magnetic phase and Ni80Fe20 (permalloy) thin films form a stripe-like magnetic domain structure above a critical thickness. This critical thickness is considerably different in the two alloys and allows us to study the influence of the magnetic coupling in the domain configuration in bilayers. Using dc magnetron sputtering techniques, we fabricated two different sets of FePt/Ni80Fe20 bilayers, keeping one thickness fixed and varying the other, and investigated the dc magnetic properties and the magnetic domain configuration of the structure. In all cases, magnetization reversal occurred at a single coercive field, indicating a relatively strong magnetic exchange coupling between both layers. The observed stripe period was also consistent with a model of spring magnet-like behavior. However, for certain values of FePt and permalloy thickness a complex nonparallel double stripe structure was found, which may be attributed to the influence of the dipolar stray field of the thicker layer on the stripe structure of the thinner film. [ABSTRACT FROM AUTHOR]

In this paper we present the development and characterization of FM/MgO/FM (FM  =  Co90Fe10, Fe20Ni80) heterostructures. The magnetic order of the structures, magnetic anisotropy and interlayer exchange coupling were characterized by magnetization measurements. The influence of the substrate temperature during growth on the magnetic properties and topographical features of the bottom electrode was also explored. Higher values of the coercive field were achieved increasing the substrate temperature during deposition of the bottom electrode. Patterned magnetic tunnel junctions were grown on Si(1 0 0) and MgO(1 0 0). The junctions consist of square pillars with different areas (1600, 625, 100 and 25 μm2) fabricated by optical lithography. I(V) curves obtained with conducting atomic force microscopy of the patterned junctions were performed at room temperature in order to explore the reproducibility of the transport properties of the insulating barrier. The results show a more insulating behavior of the junctions grown on Si(1 0 0), with very good control and a high reproducibility of the transport properties of the MgO insulating barrier. [ABSTRACT FROM AUTHOR]

We present a study of the magnetic properties of chemically disordered ferromagnetic FePt films of 100 nm thickness that have been grown by sputtering with different Ar pressures ( mTorr). We found that the residual stress can be controlled by the sputtering pressure, which in turn allows to tune the perpendicular magnetic anisotropy due to magnetoelastic effects. Films deposited at lower Ar pressures display an in-plane compressive stress that favors an out of plane component of the magnetization and the formation of a magnetic domain structure in the form of stripes. For higher pressures the stress is relaxed and the magnetic configuration changes to planar domains. These results show the possibility to accurately tune the initial magnetic state in films with potential applications in magnetoelectrically coupled devices. [ABSTRACT FROM AUTHOR]