GLASS-COATED ULTRAFINE AMORPHOUS WIRES HAVING A GIANT MAGNETO-IMPEDANCE (GMI) EFFECT AT HIGH FREQUENCIES

The invention relates to a method for producing glass-coated thin microwires (with a metal core diameter below 20 µm) displaying giant magneto-impedance (GMI) at high frequencies (above 10 MHz). The microwires are prepared using a modified Taylor-Ulitovsky method, in which the wires are produced directly from casting, as described by V. S. Larin, A. V. Torcunov, A. Zhukov, J. González, M. Vázquez, L. Panina in "Preparation and properties of glass-coated microwires" J. Magn. Magn. Mater. 249/1-2 (2002) 39-45. On a laboratory scale, a few grams of the master alloy with the desired composition are disposed inside a Pyrex glass tube which is placed in the vicinity of a high-frequency inductor heating system. The alloy is heated to the melting point thereof, thereby forming a droplet. As the metal melts, the portion of the glass tube adjacent to the melting metal softens, so as to surround the metal droplet. As a result, a capillary is obtained when the softened glass is drawn from the portion of the softened glass and wound around a rotating spool. For suitable drawing conditions, the molten metal fills the capillary glass and, in this way, a microwire is formed at the metal core, completely surrounded by a sheet of insulating glass. The composition of the metal core and the geometry (diameter of the metal core d, thickness of the glass sheet T and the corresponding ratio) determine the magnetic properties and the GMI effect. La invención consiste del método de fabricación de delgados microhilos con recubrimiento vítreo (con el diámetro del núcleo metálico inferior a 20 µm) mostrando efecto de Magnetoimpedancia Gigante (GMI) a frecuencias elevada (superior a 10 MHz). Los microhilos son preparados or medkio de un método modificado del Taylor-Ulitovsky, basado en la producción directa fdesde el fundido, tal como se describe por V. S. Larin, A. V. Torcunov, A. Zhukov, J. González, M. Vázquez, L. Panina en "Preparation and properties of glass-coated microwires" J. Magn. Magn. Mater. 249/1-2 (2002) 39-45. A escala de laboratorio, unos pocos gramos de la aleación master con la composición deseada se sitúa en el interior de un tubo de vidrio de Pyrex que se coloca en las inmediaciones de un sistema de calentamiento inductor de alta frecuencia. La aleación es calentada hasta su punto de fusión formando una gotita. Mientras el metal funde, ñ porción del tubo de vidrio adyacente al metal fundente se ablanda, envolviendo a la gotita de metal. Como resultado se obtiene un