The aim of this CAREER project is to investigate the electrical properties of nanometer-sized ferromagnetic islands separated by insulating barriers from larger ferromagnetic contacts--an extension of the single-electron device, where electrons can be added individually to a small conducting island ("Coulomb island"). The magnetoresistance observed in tunneling magnetic systems is attributed to the spin polarization of the electrons in the ferromagnetic electrodes. Changing the magnetic orientation results in a drastic variation of the junction conductance, permitting the magnetic island to play the role of a gate in a single-electron transistor device. Control of current flow will be monitored through the magnetic orientation of the island, without the necessity of an electrical gate connection. A reduction in size compared to semiconductor devices can be expected because of the larger carrier density of metals. Ultra-small devices will be fabricated by electrochemical template synthesis. Previous accomplishments on individual junctions of 0.01 mm2 area, with a 1 nm thick insulator separating two ferromagnetic half-wires will be the starting point of these studies. Specific goals of the project are: to understand the influence of impurities in the insulator, revealed by electron blockade effects and strong fluctuations of the recorded voltage; to synthesize junctions two orders of magnitude smaller; to make double junction systems, embedding an island of volume smaller than 100 nm3; to investigate systems where the island or the electron source(sink) is not ferromagnetic; and, to gain access into the spin relaxation time in the ferromagnetic island. The interdisciplinary nature of the project will be the basis for a new undergraduate laboratory course introducing students to the science of electronics. The research topics will serve as a motivating application for students at all levels. The laboratory topics will be directly derived from the research, and will introduce electrical measurements on mesoscopic systems and techniques of small signal detection. A multi-disciplinary approach will be gained by introducing undergraduate and graduate students in physics to the technique of electrochemistry. The synthesis/processing methods employed in the research can be learned by undergraduate students in a relatively short time. Electrical connections to the samples can be initially preformed without special precautions, and suitable devices can be studied immediately which provide good examples for low signal measurements, for the study of noise properties, and for understanding the differences between high and low impedance circuits. %%% The project addresses fundamental research issues in a topical area of materials science having high technological relevance. The research will contribute basic materials science, physics, and engineering knowledge at a fundamental level to important aspects of electronic materials and advanced devices/circuits. The scope of the project will expose students to challenges in materials synthesis, processing, and characterization. An important feature of the project is the strong emphasis on education, and on the integration of research and education. ***
