Atualmente, nanopartículas (NPs) são utilizadas em todos os ramos da tecnologia. Suas promissoras aplicações envolvem entre outros, o campo dos sensores e transdutores, mídia de gravação magnética, carreadores magnéticos de drogas medicinais. Com o objetivo de produzir NPs pelo método físico, um gerador de nanopartículas foi adaptado usando um dos canhões do sistema de magnetron sputtering, baseando-se no método de agregação gasosa. Com o gerador somos capazes de produzir NPs de diversos materiais e codepositá-las em matrizes dielétricas ou metálicas. Neste trabalho apresentamos o desenvolvimento da metodologia para a produção de nanopartículas de materiais magnéticos duros, usando alvos de SmCo5, Sm2Co17, Nd2Fe17B, FePt e CoPt. Investigamos a influência dos parâmetros de deposição (pressão, fluxo de gás e potência de sputtering), tipo de substrato e a existência de buffer e/ou codeposição, na obtenção das propriedades estruturais e magnéticas desejadas para esses materiais. As NPs produzidas são analisadas magneticamente pelo VSM e SQUID, sua morfologia e tamanho por TEM e SEM, a sua estequiometria pelo RBS, e a sua estrutura cristalina por XRD, a fim de obter nano-ímãs de alta anisotropia magnética. Da caracterização morfológica, através de microscopia eletrônica, encontramos para as NPs produzidas e estudadas diâmetros entre 5 e 17 nm. Através de análises de RBS obtemos para composição das NPs que as mesmas possuem estequiometria diferente dos alvos usados. Estudos estruturais e magnéticos mostram que para Sm-Co, Fe-Pt e Co-Pt é possível obter NPs cristalinas e com coercividade da ordem de 1 kOe. / In the recent years, nanoparticles (NPs) are being in all fields of technology. Their promising applications involve among others, the field of sensors and transducers, magnetic recording media, magnetic carriers of medicinal drugs. Aiming to produce NPs by physical method, a generator of nanoparticles was adapted using a system of guns \"magnetron sputtering\", based on the aggregation gas method. With the generator we are able to produce NPs with different types of material. In this work, we present the development of the methodology for the production of nanoparticles of hard magnetic materials, using targets of SmCo5, Sm2Co17, Nd2Fe17B, FePt and CoPt. We investigated the influence of the deposition parameters (pressure, gas flux and sputtering power), substrate type and the existence of the buffer and/or codeposition layers, to obtain the desired structural and magnetic properties for the nanoparticles. The produced NPs were magnetically analyzed by VSM and SQUID, the morphology and size by TEM and SEM, the stoichiometry by RBS and the crystal structure by XRD. The main objective of this work is to obtain nano-magnet with high magnetic anisotropy. Through the morphological characterization by electron microscopy, we found for NPs produced and studied have diameters between 5 and 17 nm. Through RBS analysis we have obtained the composition of the NPs, and also that they have different stoichiometry in relation to the used targets. Structural and magnetic studies have show that for Sm-Co, Fe-Pt and Co-Pt it is possible to obtain crystalline NPs with coercive field around 1 kOe.

Atualmente, nanopartículas (NPs) são utilizadas em todos os ramos da tecnologia. Suas promissoras aplicações envolvem entre outros, o campo dos sensores e transdutores, mídia de gravação magnética, carreadores magnéticos de drogas medicinais. Com o objetivo de produzir NPs pelo método físico, um gerador de nanopartículas foi adaptado usando um dos canhões do sistema de magnetron sputtering, baseando-se no método de agregação gasosa. Com o gerador somos capazes de produzir NPs de diversos materiais e codepositá-las em matrizes dielétricas ou metálicas. Neste trabalho apresentamos o desenvolvimento da metodologia para a produção de nanopartículas de materiais magnéticos duros, usando alvos de SmCo5, Sm2Co17, Nd2Fe17B, FePt e CoPt. Investigamos a influência dos parâmetros de deposição (pressão, fluxo de gás e potência de sputtering), tipo de substrato e a existência de buffer e/ou codeposição, na obtenção das propriedades estruturais e magnéticas desejadas para esses materiais. As NPs produzidas são analisadas magneticamente pelo VSM e SQUID, sua morfologia e tamanho por TEM e SEM, a sua estequiometria pelo RBS, e a sua estrutura cristalina por XRD, a fim de obter nano-ímãs de alta anisotropia magnética. Da caracterização morfológica, através de microscopia eletrônica, encontramos para as NPs produzidas e estudadas diâmetros entre 5 e 17 nm. Através de análises de RBS obtemos para composição das NPs que as mesmas possuem estequiometria diferente dos alvos usados. Estudos estruturais e magnéticos mostram que para Sm-Co, Fe-Pt e Co-Pt é possível obter NPs cristalinas e com coercividade da ordem de 1 kOe. / In the recent years, nanoparticles (NPs) are being in all fields of technology. Their promising applications involve among others, the field of sensors and transducers, magnetic recording media, magnetic carriers of medicinal drugs. Aiming to produce NPs by physical method, a generator of nanoparticles was adapted using a system of guns \"magnetron sputtering\", based on the aggregation gas method. With the generator we are able to produce NPs with different types of material. In this work, we present the development of the methodology for the production of nanoparticles of hard magnetic materials, using targets of SmCo5, Sm2Co17, Nd2Fe17B, FePt and CoPt. We investigated the influence of the deposition parameters (pressure, gas flux and sputtering power), substrate type and the existence of the buffer and/or codeposition layers, to obtain the desired structural and magnetic properties for the nanoparticles. The produced NPs were magnetically analyzed by VSM and SQUID, the morphology and size by TEM and SEM, the stoichiometry by RBS and the crystal structure by XRD. The main objective of this work is to obtain nano-magnet with high magnetic anisotropy. Through the morphological characterization by electron microscopy, we found for NPs produced and studied have diameters between 5 and 17 nm. Through RBS analysis we have obtained the composition of the NPs, and also that they have different stoichiometry in relation to the used targets. Structural and magnetic studies have show that for Sm-Co, Fe-Pt and Co-Pt it is possible to obtain crystalline NPs with coercive field around 1 kOe.

This research work focuses on the geometry and shape effects on submicron magnetic material. A web based micromagnetics program is written to model the hysteresis loop of nano magnetic samples with arbitrary geometry shapes and multiple magnetic materials. Three material samples have been modeled with this program along with nano magnets with a variety of geometric shapes. Shape anisotropy has been introduced to a permalloy ring by adding a cross-tie structure with various widths. The in-plane hysteresis loop and reversal behavior have no notable difference in direction parallel to the cross-tie, but greatly changed in perpendicular and diagonal directions. The switching field distribution is significantly reduced. The two distinct "onion" bit states of the modified ring elements are stabilized in the hysteresis in the diagonal direction. The changes in the modified rings make them better candidates for Magnetic Random Access Memory elements. Two Pac-Man elements, PM I and PM II, geometrically modified from disc and half disc respectively, are modeled. The PM I element undergoes a magnetic reversal through a two-stage mechanism that involves nucleation in the left and right middle areas followed by vortex core formation and vortex core motion in the lower middle area. The reversal process of the PM II element lacks the vortex core formation and motion stage. The switching field of the PM I and PM II elements are the same but the switching field distribution of the PM II elements is much narrower than that of the PM I element. Only the PM II element meets MRAM application requirements. The thickness dependence of the magnetic properties of a core-shell structure has been studied. The nano particles have a cobalt core and a permalloy shell. The nano spheres are the same size but with various shell thickness. Simulations reveal a multi-stage reversal process without the formation of a Bloch wall for thin-shell structure and smooth reversal process with the formation and motion of a Bloch wall for thick-shell structure. Gradual transition of the hysteresis loop patterns has been observed.

Magnetic data storing has been of great interest since 1950 when the first magnetic hard drive was fabricated. A lot has happened since then, but there is still a need for smaller and cheaper devices.  One way to achieve this is by creating nano-sized ferromagnetic areas in a thin film at room temperature, or nano-magnets. In this thesis, the aim is to fabricate and characterize novel amorphous nano-magnets. Using a chromium mask ions can be implanted in a nano-sized pattern in an amorphous iron zirconium thin film. The mask is fabricated by depositing chromium over the iron zirconium and etching the nano-structures into the chromium film.  This requires the parameters for the etching to be optimized. It is discovered the parameters change with the size and shape of the pattern. Magnetization and structural characterization were performed by using the magneto-optical Kerr effect and a magnetic force microscope. The result shows that the nano-magnets become magnetically harder than the reference sample. The study further reveals structural details for further improvements in implanted regions. / <p>Opponent: Stivan Sabir</p>