Estudio del efecto magnetocalórico en películas delgadas y heteroestructuras mixtas para el desarrollo de dispositivos de refrigeración magnética
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Comisión Nacional de Energía Atómica. Gerencia Área Académica. Gerencia Instituto Sabato
Universidad Nacional San Martin. Instituto de tecnología Sabato
Universidad Nacional San Martin. Instituto de tecnología Sabato
Resumen
El efecto magnetocalórico (EMC) se conoce como el cambio adiabático en la temperatura (∆Tad) o el cambio isotérmico en la entropía magnética (∆SM ) de un material, cuando se aplica un campo magnético externo (H). Este efecto presenta su máxima intensidad cuando la temperatura del sistema coincide con la Temperatura de Curie (Tc). Dentro de la comunidad científica existe un gran interés por el estudio del EMC ya que permite la posibilidad de pensar y diseñar nuevas máquinas frigoríficas que reemplacen a las actuales, las cuales se basan en la expansión/compresión de gases que resultan ser perjudiciales para el medio ambiente. De esta forma, con este cambio de tecnología se lograría tener refrigeradores de estado sólido que sean más compactos, más eficaces y menos nocivos para el medio ambiente. Esto también vino acompañado de una búsqueda de nuevos materiales que resulten óptimos para la refrigeración de estado sólido. Muchos materiales que presentan EMC han sido estudiados a lo largo de los años, pero en particular, las manganitas destacan entre otros compuestos tanto por presentar un EMC importante, como porque también presentan una gran flexibilidad a la hora de modificar sus propiedades magnéticas con diferentes estímulos, gracias al fuerte acoplamiento entre los diferentes grados de libertad (electrónico, magnético, estructural). Por otro lado, la física de sistemas con dimensiones reducidas también resulta de un gran interés dentro de la comunidad científica. Muchas propiedades nuevas y fascinantes emergen cuando uno trabaja dentro de la escala de los nanómetros. En esta tesis nos proponemos combinar ambos “mundos”, estudiando el EMC en películas delgadas y heteroestructuras mixtas. Para esta Tesis, se crecieron mediante la técnica de depósito por láser pulsado o ablación láser (PLD), películas delgadas de manganitas de La1−xSrxM nO3 (LSMO). Esta técnica resulta muy útil para crecer óxidos mixtos como el LSMO, ya que permite transferir la estequiometría del blanco a la película delgada depositada. Luego del crecimiento, las muestras obtenidas son caracterizadas estructural, magnética y magnetocalóricamente.
The magnetocaloric effect (EMC) is known as the adiabatic change in temperature (∆Tad) or the isothermal change in magnetic entropy (∆SM ) of a material, when an external magnetic field (H) is applied. This effect presents its maximum intensity when the temperature of the system coincides with the Curie Temperature (Tc). Within the scientific community there is great interest in the study of EMC since it allows the possibility of thinking and designing new refrigeration machines that replace the current ones, which are based on the expansion/compression of gases that turn out to be harmful to the environment. atmosphere. In this way, with this change in technology it would be possible to have solid-state refrigerators that are more compact, more efficient and less harmful to the environment. This was also accompanied by a search for new materials that are optimal for solid-state cooling. Many materials that present EMC have been studied over the years, but in particular, manganites stand out among other compounds both for presenting a significant EMC, and because they also present great flexibility when modifying their magnetic properties with different stimuli. , thanks to the strong coupling between the different degrees of freedom (electronic, magnetic, structural). On the other hand, the physics of systems with reduced dimensions is also of great interest within the scientific community. Many new and fascinating properties emerge when one works within the nanometer scale. In this thesis we propose to combine both “worlds”, studying the EMC in thin films and mixed heterostructures. For this Thesis, thin films of La1−xSrxM nO3 (LSMO) manganites were grown using the pulsed laser deposition or laser ablation (PLD) technique. This technique is very useful for growing mixed oxides such as LSMO, since it allows the stoichiometry of the target to be transferred to the deposited thin film. After growth, the samples obtained are characterized structurally, magnetically and magnetocalorically.
The magnetocaloric effect (EMC) is known as the adiabatic change in temperature (∆Tad) or the isothermal change in magnetic entropy (∆SM ) of a material, when an external magnetic field (H) is applied. This effect presents its maximum intensity when the temperature of the system coincides with the Curie Temperature (Tc). Within the scientific community there is great interest in the study of EMC since it allows the possibility of thinking and designing new refrigeration machines that replace the current ones, which are based on the expansion/compression of gases that turn out to be harmful to the environment. atmosphere. In this way, with this change in technology it would be possible to have solid-state refrigerators that are more compact, more efficient and less harmful to the environment. This was also accompanied by a search for new materials that are optimal for solid-state cooling. Many materials that present EMC have been studied over the years, but in particular, manganites stand out among other compounds both for presenting a significant EMC, and because they also present great flexibility when modifying their magnetic properties with different stimuli. , thanks to the strong coupling between the different degrees of freedom (electronic, magnetic, structural). On the other hand, the physics of systems with reduced dimensions is also of great interest within the scientific community. Many new and fascinating properties emerge when one works within the nanometer scale. In this thesis we propose to combine both “worlds”, studying the EMC in thin films and mixed heterostructures. For this Thesis, thin films of La1−xSrxM nO3 (LSMO) manganites were grown using the pulsed laser deposition or laser ablation (PLD) technique. This technique is very useful for growing mixed oxides such as LSMO, since it allows the stoichiometry of the target to be transferred to the deposited thin film. After growth, the samples obtained are characterized structurally, magnetically and magnetocalorically.