INIFTA   05425
INSTITUTO DE INVESTIGACIONES FISICO-QUIMICAS TEORICAS Y APLICADAS
Unidad Ejecutora - UE
capítulos de libros
Título:
On the Properties of Interfaces and the Propagation of Perturbations in Confined Magnetic Materials
Autor/es:
M. LETICIA RUBIO PUZZO; EZEQUIEL V. ALBANO
Libro:
Magnetic Materials: Research, Technology and Applications
Editorial:
Nova Science Publishers
Referencias:
Lugar: Nueva York; Año: 2008;
Resumen:
The properties of confined magnetic materials are relevant for the development of new devices in material science, micro- and nanotechnology, and related fields. Furthermore, these properties are often quite different from those observed in the bulk of the samples, so that their understanding posses a formidable theoretical challenge. Within this context, this article provides an extensive review on recent progress achieved in the study of the properties of interfaces and the propagation of perturbations in confined magnets.A magnetic Ising film placed in a semi-infinite slab, such that the confining walls exert short-range competing magnetic fields (h) on the confined material, undergoes a wetting transition at a  well-defined critical temperature Tw(h) such that Tw<Tcb, where Tcb is the critical temperature of the bulk. In fact, the competing fields cause the occurrence of an interface between magnetic domains of different orientation.  For T<Tw(h) (T>Tw(h)) such interface is bound (unbound) to the walls, while right at Tw(h) the interface is essentially located at the center of the film.  A similar phenomenon is also observed by confining the magnet in a corner geometry with competing surface fields. The unbinding of the interface is then the analogous counterpart of the wetting of a surface by a fluid, polymer, alloy, etc., and consequently the main conclusions of the study can be generalized to a large number of physical systems that play a key role in many technological applications, e.g., adhesion, coating, lubrication, etc.On the other hand, for each value of the surface field it is observed that, above certain critical temperature TD(h), the propagation of perturbations proceeds forever, leading to an active phase.  However, below TD(h) the propagation  stops irreversibly leading to a  frozen phase. The critical points for the onset of perturbation spreading can be evaluated, showing that the wetting transition effectively shifts the location of these critical points, which are now placed within the nonwet phase. It is found that in these confined geometries, the spatiotemporal spreading of perturbations becomes considerably enhanced by the presence of interfaces between magnetic domains of different orientation, which act as a “catalyst” for the propagation, causing an enhancement of the total affected area. As expected, the propagation of perturbations along the direction parallel to an interface is faster than in the perpendicular direction. Also, the propagation into the bulk is even slower.