{"id":12466,"date":"2018-03-09T08:58:19","date_gmt":"2018-03-09T08:58:19","guid":{"rendered":"https:\/\/www.deberes.net\/tesis\/sin-categoria\/propiedades-electricas-y-magneticas-de-sistemas-con-magnetorresistencia-colosal\/"},"modified":"2018-03-09T08:58:19","modified_gmt":"2018-03-09T08:58:19","slug":"propiedades-electricas-y-magneticas-de-sistemas-con-magnetorresistencia-colosal","status":"publish","type":"post","link":"https:\/\/www.deberes.net\/tesis\/fisica\/propiedades-electricas-y-magneticas-de-sistemas-con-magnetorresistencia-colosal\/","title":{"rendered":"Propiedades electricas y magneticas de sistemas con magnetorresistencia colosal"},"content":{"rendered":"<h2>Tesis doctoral de <strong> Mar\u00eda  Jose Calderon Prieto <\/strong><\/h2>\n<p>Hemos estudiado la perovskitas de oxido de manganeso (o manganitas) y otros oxidos magneticos con magnetorresistencia colosal. Nos hemos centrado principalmente en el modelo de doble intercambio, su alcance y sus limitaciones. El doble intercambio subyace las propiedades de las manganitas y se ha mostrado que es valido por si mismo en aquellos regimenes en los que domina sobre otras interacciones.  este es el caso de las manganitas con banda de conducci\u00f3n como el la1-x sr xmno3 en el regimen de dopaje optimo y las propiedades a bajas temperaturas, donde no se espera que los grados de libertad de la red sean importantes. en el regimen de dopaje optimo, las manganitas son ferromagn\u00e9ticas y metalicas a baja temperatura y paramagneticas y aislantes a altas temperaturas.  hemos estimado la temperatura critica de la transici\u00f3n magn\u00e9tica tc por medio de una simulaci\u00f3n de monte carlo. No s\u00f3lo hemos determinado una tc dentro del rango de la experimental sino tambien la influencia de las fluctuaciones de espin( que no est\u00e1n incluidas en los tratamientos a campo medio) en su valor. Tambi\u00e9n hemos estudiado el transporte y hemos comprobado que el modelo de doble intercambio no da por si solo la transici\u00f3n metal-aislante.  despu\u00e9s de determinar las propiedades magn\u00e9ticas y electricas en el volumen, hemos estudiado las superficies de estos sistemas. Debido a la deficiencia de oxigeno en la superficie, los orbitales que participan en la conduccion dejan de estar degenerados y el mecanismo de doble intercambio se hace m\u00e1s debil. Aparecen correlaciones antiferromagneticas en la superficie por lo que la magnetizacion se suprime mucho m\u00e1s rapido con la temperatura que en el volumen. La conductancia tambien disminuye.  a bajas temperaturas, las propiedades de transporte van a venir dadas principalmente por los grados de libertad de espin, es decir, por el doble intercambio. a bajas temperaturas, las manganitas son medio metalicas y eso determin<\/p>\n<p>&nbsp;<\/p>\n<h3>Datos acad\u00e9micos de la tesis doctoral \u00ab<strong>Propiedades electricas y magneticas de sistemas con magnetorresistencia colosal<\/strong>\u00ab<\/h3>\n<ul>\n<li><strong>T\u00edtulo de la tesis:<\/strong>\u00a0 Propiedades electricas y magneticas de sistemas con magnetorresistencia colosal <\/li>\n<li><strong>Autor:<\/strong>\u00a0 Mar\u00eda  Jose Calderon Prieto <\/li>\n<li><strong>Universidad:<\/strong>\u00a0 Aut\u00f3noma de Madrid<\/li>\n<li><strong>Fecha de lectura de la tesis:<\/strong>\u00a0 20\/07\/2001<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<h3>Direcci\u00f3n y tribunal<\/h3>\n<ul>\n<li><strong>Director de la tesis<\/strong>\n<ul>\n<li>Luis Brey Abalo<\/li>\n<\/ul>\n<\/li>\n<li><strong>Tribunal<\/strong>\n<ul>\n<li>Presidente del tribunal: Francisco Guinea l\u00f3pez <\/li>\n<li>neil Mathur (vocal)<\/li>\n<li> Garcia hernandez M\u00aa del mar (vocal)<\/li>\n<li> De teresa nogueras Jos\u00e9 Mar\u00eda (vocal)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Tesis doctoral de Mar\u00eda Jose Calderon Prieto Hemos estudiado la perovskitas de oxido de manganeso (o manganitas) y otros oxidos [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center 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