Leiva, Livio (2017) Efectos magnetoeléctricos en heteroestructuras ferromagneto Pb(Mg_1/3Nb_2/3)O_3-PbTiO_3 (PMT-PT). / Magnetoelectric effects in ferromagnet Pb(Mg_1/3Nb_2/3)O_3-PbTiO_3 (PMT-PT). Maestría en Ciencias Físicas, Universidad Nacional de Cuyo, Instituto Balseiro.
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Resumen en español
Los sistemas multiferroicos han sido de gran interpes en los años recientes por sus potenciales aplicaciones tecnologicas derivadas de la coexistencia de propiedades ferroel ectricas y ferromagneticas. En particular, heteroestructuras laminares que combinan capas de materiales ferroelectricos y ferromagneticos han sido propuestas para producir el acople magnetoelectrico mediado por deformacion. En el presente trabajo se busco maximizar este efecto fabricando heteroestructuras que combinen un material ferroel ectrico de altas prestaciones piezoelectricas como son los sustratos monocristalinos de Pb(Mg_1/3Nb_2/3)O_3-PbTiO_3 (PMN-PT) con peliculas delgadas de los ferromagnetos FePt, Co, Ni, Py y FeGa, algunos de ellos altamente magnetostrictivos. En estos sistemas se busco medir la capacidad de modicar, a partir de un campo electrico aplicado al sustrato y la deformacion consecuente, las propiedades magneticas de las peliculas ferromagneticas. Con esto en mente, se realizo primero una caracterizacion general de diversas propiedades fisicas relevantes del sustrato como son la deformacion piezoel electrica, el ciclo ferroelectrico y otras propiedades estructurales. Del mismo modo, se estudiaron propiedades magneticas de los films depositados como el lazo de histeresis, la estructura de dominios y las anisotropas magneticas presentes, obteniendo informacion del sistema en ausencia del acople mediado por deformacion. Posteriormente se realizo una caracterizacion magnetoelectrica. Usando la tecnica de magnetometra de efecto Kerr magneto-optico, se estudio el cambio de la magnetizaci on remanente de las peliculas cuando se aplicaba un campo electrico al sustrato. Analizando los lazos de histeresis en el plano del film se logro estimar un campo magnetico de anisotropa debido a la deformacion del film. Tambien se midieron directamente estos campos de anisotropa a partir de experimentos de resonancia ferromagnetica. Se propuso un modelo para estas anisotropas a partir de la energa magnetoelastica y se simulo la dependencia de los campos de resonancia en funcion del campo electrico, coincidiendo cualitativamente con las medidas realizadas. Se cuantico la magntitud del acople magnetoelectrico en los distintos materiales a traves de un coeficiente derivado de la pendiente de las curvas del campo de anisotropa en funcion del campo electrico, y se propuso una forma de estimarlo a partir de propiedades macroscopicas de los ferromagnetos. Se observaron procesos irreversibles en las peliculas asociadas al sustrato que deterioraban los sistemas medidos. Tambien se investigo el fenomeno de spin pumping esperado en estos sistemas en la condicion de resonancia y se logro medir la tension de efecto Hall de espin y su dependencia con el campo electrico. Por ultimo, se presentan resultados de un fenomeno de electro-resistencia gigante observado en peliculas de FeGa.
Resumen en inglés
Multiferroic systems have been of great interest in recent years due to their potential technological applications derived from the coexistence of ferroelectric and ferromagnetic properties. In particular, laminar heterostructures that combine layers of ferroelectric and ferromagnetic materials have been proposed to produce the strain-mediated magnetoelectric coupling. In the present work we sought to maximize this eect by fabricating heterostructures that combine a ferroelectric material of high piezoelectric performance such as monocrystalline substrates of Pb Pb(Mg_1/3Nb_2/3)O_3-PbTiO_3 (PMN-PT) with thin lms of the ferromagnets FePt, Co, Ni, Py and FeGa, some of them highly magnetostrictive. In these it is desired to measure the ability to modify, through the application of an electric field to the substrate and the consequent strain, the magnetic properties of the ferromagnetic lms. With this in mind, a general characterization of several relevant physical properties of the substrate, such as piezoelectric strain, ferroelectric cycle and other structural properties, was first performed. In the same way, magnetic properties of deposited lms were studied, such as the hysteresis loop, the domain structure and the magnetic anisotropies present, obtaining information about the heterostructures in the absence of strain-mediated coupling. Subsequently, a magnetoelectric characterization was carried out. Using the magnetooptical Kerr effect magnetometry technique, the change on the remanent magnetization of the films when an electric eld was applied to the substrate was studied. Analyzing the hysteresis loops in the lm plane it was possible to estimate an anisotropy magnetic field due to the strain state of the lm. These anisotropy elds were also measured directly from ferromagnetic resonance experiments. A modeling of these anisotropies from the magnetoelastic energy was proposed and a simulation of the dependence of the resonance fields as a function of the electric eld was performed, coinciding qualitatively with the measurements made. The magnitude of the magnetoelectric coupling in diefferent materials was quantied through a coefficient derived from the slopes of the anisotropy fields curves as a function of electric field, and a way to estimate it from the macroscopic properties of ferromagnets was proposed. Irreversible processes were observed in the films, associated with the substrate, that deteriorated the measured systems. The spin pumping phenomenon expected in these systems for the resonance condition was also investigated and it was possible to measure the spin Hall effect voltage and its dependence with the electric field. Finally, results of a giant electroresistence phenomena observed in FeGa films are presented.
| Tipo de objeto: | Tesis (Maestría en Ciencias Físicas) |
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| Palabras Clave: | Piezoelectricity; Piezoelectricidad; Thin films; Capas delgadas; [Magnetoelectric heteroestructures; Heteroestructuras magnetoeléctricas] |
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| Materias: | Física > Materia condensada |
| Divisiones: | Gcia. de área de Investigación y aplicaciones no nucleares > Gcia. de Física > Ciencias de materiales > Resonancias magnéticas |
| Código ID: | 683 |
| Depositado Por: | Tamara Cárcamo |
| Depositado En: | 28 May 2018 14:38 |
| Última Modificación: | 28 May 2018 14:38 |
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