Tunable Magnetic Nanostructures: Property Characterization and Modeling

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The objectives of this proposed three year research project on Tunable Magnetic Nanostructures: Property Characterization and Modeling are: (1) to synthesize and process electronically tunable magnetic nanostructures and characterize their magnetic properties as a function of material variables and applied electric field using leading-edge characterization tools and complemented by theoretical modeling; (2) to use the results to gain a fundamental understanding on the effects of electric field, chemistry, and microstructure on properties; and (3) to advance their use in a wide range of technological applications, including magnetic data storage and magnetic sensors. Within the context of this proposed program, tunable nanostructures are defined as those metal or conducting oxide material systems that are characterized by high specific surface areas and whose magnetic properties can be “tuned” by an applied electrostatic field.This program is proposed as a German-American joint effort, involving George Washington University (GWU), Washington, DC with the assistance of National Institute of Standards and Technology (NIST), Gaithersburg, MD, and the Institute of Nanotechnology (INT), Karlsruhe, Germany. This multidisciplinary project is structured so as to judiciously exploit the complimentary and reinforcing suite of expertise and experience of the different groups as well as the advanced material synthesis and characterization tools that are available at the GWU and INT research institutions with the assistance of NIST. Specifically, the structure of the different research tasks to achieve the project goals and objectives will be distributed based on the respective expertise and experience as well as the research tools available in each establishment. Accordingly, INT will synthesize and process the tunable nanostructures, employing its pioneering novel and versatile fabrication strategies and use its in-house expertise on Mössbauer spectroscopy to examine the local crystallographic structure and charge state of each tunable sample. Similarly, GWU and NIST will characterize the magnetic properties (MS, MR, HC, Hb, and TC and FORC reversible curves) by the advanced measurement tools, including a SQUID VSM, equipped with a space heater, allowing measurements from 1.8 K to 1000 K to an applied field up to 7 T. GWU with assistance of NIST will also characterize the chemistry, structure, and microstructure, using advanced electro-optical techniques, including a Titan scanning transmission electron microscope equipped with Lorentz microscopy and electron tomography capabilities as well conduct Kerr magneto-optical spectroscopy with an electro-chemical cell; the modeling effort will be carried out by the US team, utilizing a Preisach approach. The tunable nanostructures selected for this project are: Fe1-xRhx and FeRh1-xPtx alloys. The rationale for selecting these alloys will be given in the body of the proposal. The planning and execution of this proposed project has been and will be highly interactive among the US and German team members. The planning for carrying out the different project tasks will be agreed upon and coordinated in real-time via e-mail and telephone calls. Exchanged visits between the US and German team members will be arranged when they are needed. Being that the outreach component will be an essential element of the project, student exchanges will be arranged on a mutually agreeable basis. That is, a German graduate student or a post-doctoral fellow would spend a period of time (three to six months) at the US research institutions and vice versa for American students at INT. The chances for success of this project are enhanced by the mix of the assembled team whose key members have known each other for a number of years and have collaborated in the past in a number of research projects. This proposed project is a highly integrated collaborative effort involving three leading research institutions in the areas of nanotechnology, magnetism, and magnetic materials. The funding sought for the project from NSF will be for GWU, whereas INT will seek its funding from DFG in Germany. In the following sections of the proposal the details of scientific motivation, an overview of the experimental technique and associated equipment are given as well as a description of the program structure.