Electric Field Effects on the Ferromagnetism of Dynamically Phase Separated Manganites

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Non-technical AbstractThis award from the Division of Materials Research supports the University of Florida with a project to study the effect of electric fields on the magnetism in a class of materials called manganites. Manganites can exist in various magnetic phases known as ferromagnetic, antiferromagnetic, and paramagnetic and can even form a phase separated state in which these magnetic phases coexist. The principal investigator and his research team of graduate and undergraduate students grow crystalline thin films of manganites and control their phase separated state to form nanometer to micrometer sized ferromagnetic regions embedded in an antiferromagnetic insulating matrix. The samples are then subjected to external stress and electric field and the effect on the ferromagnetic regions is measured using techniques such as microscopy and neutron reflectometry. A possible outcome of this project is the control of the magnetism in using an electric field, which could lead to data storage devices with reduced energy consumption. Since this project includes both sample preparation and measurement, young scientists are trained to use a broad array of modern experimental techniques and the expertise acquired enhances their future career options in both the industry and academe.Technical AbstractPerovskite manganese oxides (manganites) exhibit competing phases with different electronic, magnetic, and structural properties which can result in phase coexistence. In high-quality thin films of manganites the coexistent phases have shown evidence that they behave in a dynamic and fluid-like manner and can even move spatially within the solid sample under the influence of strain and electric field. This project investigates this fluid-like behavior in manganites and its possible application to control the magnetic properties of the material with an electric field. The experiments are designed to: (1) ascertain the physical mechanism behind the fluid-like behavior of the ferromagnetic regions in the dynamic phase coexistence state and hence, find the optimal conditions for producing such a state, (2) investigate the effects of electric field, strain, and sample geometry on the dynamic phase separated state, and (3) measure the effect of an electric field on the magnetic properties. The high-quality thin films of manganites are grown using pulsed laser deposition. The local and bulk properties of the thin films and fabricated micro/nanostructures are then studied using techniques such as low temperature conducting atomic force microscopy, spin-polarized neutron reflectometry, resistivity, and magnetization measurements. Density functional theory calculations are used to model the experimental results and suggest new directions for the experimental efforts. The results of this project are expected to reveal a novel method for generating an electric field effect on the magnetic properties of a material. Since this project includes both sample preparation and measurement, young scientists are trained to use a broad array of modern experimental techniques and the expertise acquired enhances their future career options in both the industry and academe.