{"id":6,"date":"2016-02-25T12:36:11","date_gmt":"2016-02-25T11:36:11","guid":{"rendered":"http:\/\/blog.uclm.es\/apnano\/?page_id=6"},"modified":"2022-10-19T07:09:22","modified_gmt":"2022-10-19T07:09:22","slug":"research-lines","status":"publish","type":"page","link":"https:\/\/blog.uclm.es\/apnano\/research-lines\/","title":{"rendered":"Research lines"},"content":{"rendered":"\n<ul class=\"has-black-color has-text-color has-large-font-size wp-block-list\"><li><strong style=\"font-family: Bitter, Georgia, serif;font-size: 22px\">Magnetic Nanoparticles<\/strong><\/li><\/ul>\n\n\n\n<p>A Web of Science search reveals thousands of articles published in the technologically and fundamentally important field of \u201cinteracting magnetic particles\u201d, with a significant fraction of these dealing with how dipolar interparticle interactions in disordered particle systems may lead to spin-glass-like behaviour. In 2013 we presented a first model superspin-glass [1]: a nanoparticle ensemble exhibiting magnetic behaviour previously observed only in conventional spin-glasses*. This was achieved by preparing a material that \u201coptimizes\u201d (maximizes and yet limits the distribution of) dipolar interparticle interactions through tailoring of the spatial homogeneity and size distribution of nanoparticles. Namely, we realized a dense random assembly (close to the random-close-packed configuration, corresponding to the maximum possible particle volume fraction, as shown in the figure below) of higly uniform oxide nanoparticles. Recent progress in material science, which has facilitated the synthesis of large batches of identical (within less than 2-3 % of the mean diameter) nanoparticles, was instrumental in this realization of what may be considered the closest nanoparticle analogue (driven by dipolar interactions) of a conventional magnetically ordered state (driven by exchange) reported to date.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"383\" height=\"308\" src=\"https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_superspin_glasses1.jpg\" alt=\"\" class=\"wp-image-213\" srcset=\"https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_superspin_glasses1.jpg 383w, https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_superspin_glasses1-300x241.jpg 300w\" sizes=\"auto, (max-width: 383px) 100vw, 383px\" \/><\/figure>\n\n\n\n<p>More over, by comparing our model compact system with other, less concentrated, ensembles of the same particles coated with silica shells [2] (see TEM micrograph below), as well as with other compacts made with uniform particles of different sizes [3], we have provided answers to the fundamental question as to the relative importance of interparticle superexchange versus dipolar interaction between oxide magnetic particles in direct physical contact. In a broad sense, the study of interparticle interactions, sometimes leading to superspin-glass or to superferromagnetic behavior, is partly motivated by the technological applications of dense magnetic NP ensembles, ranging from magnetic storage to cancer therapies based on magnetic particles and sometimes relying on interparticle interactions. The experimental techniques employed in this research line are, among others, SQUID magnetometry, TEM and HRSEM microscopy, and small-angle x-ray scattering (SAXS).<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"409\" height=\"298\" src=\"https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_superspin_glasses2.jpg\" alt=\"\" class=\"wp-image-214\" srcset=\"https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_superspin_glasses2.jpg 409w, https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_superspin_glasses2-300x219.jpg 300w\" sizes=\"auto, (max-width: 409px) 100vw, 409px\" \/><\/figure>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"251\" height=\"250\" src=\"https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_superspin_glasses3.jpg\" alt=\"\" class=\"wp-image-104\" srcset=\"https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_superspin_glasses3.jpg 251w, https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_superspin_glasses3-150x150.jpg 150w\" sizes=\"auto, (max-width: 251px) 100vw, 251px\" \/><\/figure>\n\n\n\n<ul class=\"has-text-color has-medium-font-size wp-block-list\" style=\"color:#050505\"><li><strong>Exchange bias in nanostructures<\/strong><\/li><\/ul>\n\n\n\n<p>Exchange coupling between an antiferromagnet (or a random magnet) and a nanoscale ferro- or ferrimagnet may yield a significantly enhanced magnetic rigidity (anisotropy) of the latter. This is most commonly observed as a horizontal shift in the hysteresis loop measured under certain protocols (the shift is referred to as \u201cexchange bias\u201d). Exchange bias is extensively exploited in the so-called spin-valves, the magnetoresistive reading sensors in everyday hard disk write\/read heads; however, and despite being known since decades, it is still a challenging effect to understand from a fundamental point of view. In the ApNano group we explore exchange bias in a variety of nanostructures, including multilayered thin films [1] and nanoparticles [2]. In the latter case, this research line thus deals with \u201cintraparticle (core-shell) interactions\u201d, which complements the line on \u201cinterparticle interactions\u201d. In most real systems of the ubiquitous Fe-oxide nanoparticles, both intra- and inter-particle interactions are present.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"438\" height=\"365\" src=\"https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_exchange_bias.jpg\" alt=\"\" class=\"wp-image-100\" srcset=\"https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_exchange_bias.jpg 438w, https:\/\/blog.uclm.es\/apnano\/wp-content\/uploads\/sites\/37\/2016\/02\/APNANO_exchange_bias-300x250.jpg 300w\" sizes=\"auto, (max-width: 438px) 100vw, 438px\" \/><\/figure>\n\n\n\n<p>&nbsp;<\/p>\n\n\n\n<p>In the context of magnetic nanoparticles, exchange coupling has been suggested as a strategy to delay the superparamagnetic limit. If one takes a fridge magnet (or, for the same purpose, a bit of information from our hard drives) and shrinks it sufficiently (down to the nanometer range), the thermal energy in the room will be enough to make the north and south poles flip millions of times per second (i.e., the magnet will be in the superparamagnetic regime). This renders the nanomagnets useless, since they can no longer retain a fixed magnetization in the absence of applied magnetic field, which is the basis of permanent magnets and magnetic recording. In other words, the miniaturization race in certain magnetic devices is doomed to end at the \u201csuperparamagnetic limit\u201d abyss. A successful approach to push this limit further down in size was reported years ago in the journal Nature [3], in which small ferromagnetic nanoparticles were stabilized by coupling them to an antiferromagnet. The downside was that the stabilizing effect ceased at a still low 15 \u00baC, which makes the effect impractical. In 2015, the ApNano group (in collaboration with researchers at Barcelona and Grenoble) reported the preparation of a superior artificial antiferromagnet (capable of stabilizing small nanomagnets beyond 120 \u00baC) through the convenient hybridization of the properties of two naturally occurring antiferromagnets (cobalt oxide and nickel oxide) via a proximity mechanism, and proposed a model that explains the nature of such an effect [2].<\/p>\n\n\n\n<p><span style=\"color: #000000\"><strong>[1] Influence of spacer layer morphology on exchange bias properties of reactively sputtered Co\/Ag multilayers<\/strong><br>P. S. Normile et al., <a href=\"http:\/\/journals.aps.org\/prb\/abstract\/10.1103\/PhysRevB.76.104430\">Physical Review B 76, 104430 (2007)<\/a>.<\/span><span style=\"color: #000000\"><br><strong>[2] High temperature magnetic stabilization of cobalt nanoparticles by an antiferromagnetic proximity effect <\/strong><br>J.A. de Toro et al., <a href=\"http:\/\/journals.aps.org\/prl\/abstract\/10.1103\/PhysRevLett.115.057201\">Physical Review Letters 115, 057201 (2015)<\/a>.<br><strong>[3] Beating the superparamagnetic limit with exchange bias <\/strong><br>V. Skumryev et al., <a href=\"http:\/\/www.nature.com\/nature\/journal\/v423\/n6942\/full\/nature01687.html\">Nature 423, 850 (2003)<\/a>.<\/span><\/p>\n\n\n\n<ul class=\"has-black-color has-text-color has-large-font-size wp-block-list\"><li><strong> Education &amp; Communication <\/strong><\/li><\/ul>\n\n\n\n<p>&nbsp;<\/p>\n\n\n\n<p>Diversos miembros del grupo hemos llevado experiencias de F\u00edsica a las Semanas de la Ciencia, organizadas por la UCLM, y participado en las Noches de los investigadores, en <em>Pint of Science<\/em> y en las Jornadas de Puertas Abiertas del Instituto Regional de Investigaci\u00f3n Cient\u00edfica.<\/p>\n\n\n\n<p>Jos\u00e9 A. De Toro ha sido tambi\u00e9n colaborador del portal web de divulgaci\u00f3n www.cienciaes.com y participado en cursos de verano en distintas universidades. Pablo Mu\u00f1iz y otros profesores del grupo han visitado institutos de secundaria bajo la organizaci\u00f3n del Departamento de F\u00edsica Aplicada para dar charlas divulgativas.<\/p>\n\n\n\n<p>Adem\u00e1s, nuestro inter\u00e9s por la ense\u00f1anza de la F\u00edsica general nos ha llevado a realizar estudios que han dado lugar a una publicaci\u00f3n en&nbsp; una revista indexada del \u00e1rea Physics Education.&nbsp;<\/p>\n\n\n\n<p>&#8211; Jose A. De Toro, Gabriel F. Calvo, and Pablo Mu\u00f1iz, \u201cTwo-Dimensional Crystallography Introduced by the Sprinkler Watering Problem.\u201d European Journal of Physics 33(1), 167\u2013177 (2012).<\/p>\n\n\n\n<div style=\"height:34px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<ul class=\"has-black-color has-text-color wp-block-list\" style=\"font-size:18px;font-style:normal;font-weight:700\"><li>Estrategia de Especializaci\u00f3n Inteligente de Castilla-La Mancha (RIS3 CLM)<\/li><\/ul>\n\n\n\n<p>En cuanto a la organizaci\u00f3n y participaci\u00f3n en actividades de innovaci\u00f3n docente, varios miembros del grupo hemos participado en cursos de Ense\u00f1anza de la F\u00edsica al profesorado de Educaci\u00f3n Secundaria y Bachillerato que han sido organizados por la Junta de Comunidades de Castilla-La Mancha y\/o la UCLM.<\/p>\n\n\n\n<p>Adem\u00e1s, Pablo Mu\u00f1iz ha sido organizador de la XXXII Reuni\u00f3n Bienal de la Real Sociedad Espa\u00f1ola de F\u00edsica y 19\u00ba Encuentro Ib\u00e9rico de Ense\u00f1anza de la F\u00edsica (Ciudad Real, 7-11 de septiembre de 2009). Varios miembros del grupo presentaron contribuciones en este evento.<\/p>\n\n\n\n<ul class=\"has-black-color has-text-color has-medium-font-size wp-block-list\"><li><strong> Estrategia de Especializaci\u00f3n Inteligente de Castilla-La Mancha (RIS3 CLM) <\/strong><\/li><\/ul>\n\n\n\n<p>Las l\u00edneas de investigaci\u00f3n del grupo Apnano de la UCLM est\u00e1n en consonancia con los objetivos del Programa Operativo Plurirregional de Espa\u00f1a y de la Estrategia de investigaci\u00f3n e innovaci\u00f3n para la especializaci\u00f3n inteligente RIS3 de Castilla-La Mancha. Nuestra actividad investigadora financiada est\u00e1 orientada a las aplicaciones de energ\u00eda y de sensores con nuevos materiales magn\u00e9ticos de mucha incidencia en diversos sectores estrat\u00e9gicos, en particular los sectores estrat\u00e9gicos 4 (Aeron\u00e1utica) y 5 (Medio Ambiente y Energ\u00eda) de la RIS3 de Castilla La Mancha. Adem\u00e1s de la generaci\u00f3n de conocimiento, nuestra actividad ha estado tambi\u00e9n dirigida a la transferencia de resultados, con patente y una licencia de patente productiva. En la regi\u00f3n y en el territorio nacional hay empresas con las que colaborar en caso de volver a patentar, quiz\u00e1s un nuevo m\u00e9todo de s\u00edntesis, nueva instrumentaci\u00f3n o la propuesta de un nuevo sensor magnetorresistivo o de magnetoimpendancia. Nuestro grupo tiene actualmente dos ejes de actividad investigadora, que a continuaci\u00f3n encuadramos en dichos sectores estrat\u00e9gicos.<\/p>\n\n\n\n<p>&#8211; Los nuevos sensores en relaci\u00f3n a los sectores estrat\u00e9gicos 4 y 5:<br>Los sensores magnetorresistivos y de magnetoimpedancia est\u00e1n presentes en muchos sectores, algunos muy avanzados como la avi\u00f3nica, la rob\u00f3tica y los sistemas cognitivos, otros de mucha implantaci\u00f3n como la generaci\u00f3n y\/o conversi\u00f3n de energ\u00eda, veh\u00edculos, telefon\u00eda m\u00f3vil, seguridad y otras industrias. Los materiales sensores que estudiamos son punteros, pues su dise\u00f1o a\u00fana una robusta geometr\u00eda de nanohilos planos cuasi-paralelos, un intenso efecto magnetorresistivo, y marcadas anisotrop\u00edas controlables, permitiendo as\u00ed combinar una alt\u00edsima sensibilidad tanto a la intensidad como a la direcci\u00f3n del campo magn\u00e9tico. Adem\u00e1s, no menos importante es la obtenci\u00f3n de estos sistemas materiales sobre un soporte flexible, ligero y transparente, pues as\u00ed son entonces de inter\u00e9s para dispositivos electr\u00f3nicos flexibles y otras tecnolog\u00edas emergentes.<\/p>\n\n\n\n<p>&#8211; Los nuevos imanes permanentes en relaci\u00f3n a el sector estrat\u00e9gico 5:<br>De otro lado, la necesidad de nuevos imanes permanentes con mejores propiedades es enorme, al usarse sistem\u00e1ticamente en los alternadores de las turbinas de aerogeneradores y centrales convencionales, as\u00ed como en los motores de coches el\u00e9ctricos. Una mejora del 1% en la conversi\u00f3n energ\u00e9tica resultar\u00eda, s\u00f3lo en la Uni\u00f3n Europea, en ahorros anuales de aprox. 1000 millones de euro y en una reducci\u00f3n de las emisiones de CO2 equivalente a millones de toneladas de carbono. Pero no s\u00f3lo interesa un nuevo material magn\u00e9tico con mejor eficiencia energ\u00e9tica sino tambi\u00e9n que no contenga materiales cr\u00edticos. En particular, la reducci\u00f3n o eliminaci\u00f3n de tierras raras en las turbinas e\u00f3licas tendr\u00eda especialmente un impacto en Castilla-La Mancha, regi\u00f3n donde esta industria est\u00e1 se\u00f1alada entre las prioridades S3P de la comisi\u00f3n europea. Debemos apuntar que cada turbina e\u00f3lica requiere el empleo de unos 600 kg de Nd2Fe14B por megavatio de potencia instalada (por tanto, cientos de kilogramos de neodimio; un material cr\u00edtico para la UE por su importancia tecnol\u00f3gica y riesgo de suministro).<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Magnetic Nanoparticles A Web of Science search reveals thousands of articles published in the technologically and fundamentally important field of \u201cinteracting magnetic particles\u201d, with a significant fraction of these dealing with how dipolar interparticle interactions in disordered particle systems may lead to spin-glass-like behaviour. In 2013 we presented a first model superspin-glass [1]: a nanoparticle &hellip; <a href=\"https:\/\/blog.uclm.es\/apnano\/research-lines\/\" class=\"more-link\">Seguir leyendo <span class=\"screen-reader-text\">Research lines<\/span> <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":194,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-6","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/blog.uclm.es\/apnano\/wp-json\/wp\/v2\/pages\/6","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.uclm.es\/apnano\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/blog.uclm.es\/apnano\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/blog.uclm.es\/apnano\/wp-json\/wp\/v2\/users\/194"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.uclm.es\/apnano\/wp-json\/wp\/v2\/comments?post=6"}],"version-history":[{"count":2,"href":"https:\/\/blog.uclm.es\/apnano\/wp-json\/wp\/v2\/pages\/6\/revisions"}],"predecessor-version":[{"id":1283,"href":"https:\/\/blog.uclm.es\/apnano\/wp-json\/wp\/v2\/pages\/6\/revisions\/1283"}],"wp:attachment":[{"href":"https:\/\/blog.uclm.es\/apnano\/wp-json\/wp\/v2\/media?parent=6"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}