The Effect of Strain on the Phase Separation and Magnetoelectric Coupling in Manganites

University Of Florida, Gainesville FL

Investigators

Abstract

NON-TECHNICAL ABSTRACT Multiferroics are compounds which can be simultaneously magnetized (are ferromagnetic) and electrically charged (are ferroelectric). Such compounds hold promise for applications in devices and lead to unprecedented data-storage capacity. However, the underlying mechanism which leads to such unique properties is poorly understood and needs to be resolved before practical devices can be fabricated. This individual investigator award supports the study of a family of multiferroic manganese oxide compounds known as manganites. The properties of manganites are intimately linked to their crystal structure. The theme of this project is to quantify the role played by crystal structure in multiferroic manganites and suggest methods to design materials better suited for device applications. High quality manganite thin films will be grown using laser ablation. These thin films' response to strain (change in the crystal structure) will be studied by measuring the change in their electrical resistance and magnetism. The microscopic effect of strain will be studied using techniques such as a microscope capable of mapping the local magnetism of the material. Since the research and training program includes both sample preparation and measurement, this award will help train undergraduate and graduate students in various aspects of condensed matter physics research and give them a broad based experience, which will enhance their future career options in the industry or academe. TECHNICAL ABSTRACT Perovskite manganese oxides (manganites) display unique properties such as micrometer scale phase separation and multiferroism, which are intimately linked to their crystal structure. Hence, the electrical and magnetic properties of manganites are sensitive to strain. This individual investigator award supports an experimental program to directly measure the effect of strain on the properties of manganites and by comparing the results to the predictions of theoretical models, determine the origin of phase separation and multiferroism in manganites. The experimental results are also expected to reveal methods of enhancing the magnetoelectric coupling in multiferroic manganites and controlling the nanoscale properties of phase separated manganites. High quality manganite thin films will be grown using pulsed laser deposition. The thin films will then be subjected to direct external stress using a three point beam-bending apparatus to induce uniaxial strain in the material. Using a complementary suite of local and bulk measurement techniques such as magnetotransport, magnetization, scanning probe microscopy, and neutron reflectometry, the phase diagram of the thin films will be mapped as a function of strain, magnetic field, electric field, and temperature. Since the research and training program includes both sample preparation and measurement, undergraduate and graduate students will be able to learn about a wide variety of materials and experimental techniques, which will prepare them for academic and industrial careers.