Exploring Phase Separation in Manganite Films

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Technical Abstract In order to understand the origin and properties of the observed phase coexistence in manganites, this project will measure the magnetic, electronic and structural properties of manganite films on multiple length scales under strain and under pressure. High resolution x-ray diffraction measurements will be applied to determine the lattice parameters of the film components and the substrates. In parallel, the local structure and valence about the transition metal atoms and the oxygen atoms will be determine. In addition to bulk magnetization measurements, detailed magnetic imaging of the surface will be conducted by photoexcitation electron emission microscopy (PEEM) measurements. Patterned films will be examined to explore geometrical effect. The film results will be compared with parallel magnetization and high pressure transport and structural measurements on the corresponding bulk samples. In this way, we will be able to separate extrinsic effects from intrinsic effect as well to explore changes at the surface of manganites in comparison with bulk samples. Graduate and undergraduate students will be involved in all levels of this work including sample preparation, laboratory and synchrotron based measurements, modeling and data analysis. A seven week summer research and teaching program on transition metal oxide preparation and characterization, designed for Newark area high school students will be continued and expanded to include a two-week workshop for high school teachers to enable them to implement components of the program into their laboratory experiments. Non-Technical Abstract Manganite oxides exhibit significant changes in electrical conductivity in response to pressure, magnetic fields, light, and electrical fields. As a result of this sensitivity, these materials show much promise for the development of new magnetic sensors and non-volatile data storage. However, much basic research is needed in order to truly understand the origin of the response to external stimuli and to optimizer them for applications. Understanding phase coexistence is a central part of the required basic research. This project will measure the magnetic, electronic and structural properties of manganite films on multiple length scales under strain and under pressure to fully characterize the response to external perturbations. Synchrotron based x-ray methods will be used to determine the structure, valence and magnetic properties. The results will lead to more detailed models of these materials, and possibly, methods for optimizing them in applications. Graduate and undergraduate students will be involved in all levels of this work including sample preparation, laboratory and synchrotron based measurements, modeling and data analysis. A seven week summer research and teaching program on transition metal oxide preparation and characterization, designed for Newark area high school students will be continued and expanded to include a two-week workshop for high school teachers to enable them to implement components of the program into their laboratory experiments. The program will be integrated into high school science laboratory courses. This will serve to (1) develop scientific literacy and to directly influence students to pursue careers in science, and (2) provide exposure to experimental techniques and methods to high school teachers and high school students and to others who do not have access to modern research facilities.