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Combinatorial Synthesis and Characterization of Magnetic Alloys

Synthesis of new alloys and compounds holds one of the keys to scientific and technological advances. This is particularly true in electronics materials, where finding the materials that can generate and filter spin polarized electrons is critically important for developing the next generation spin polarized electronics, 'spintronics'. Since the Stone Age, materials have been synthesized and studied one at a time, but this 'hit or miss' process is becoming exceedingly difficult owing to the complex nature of candidate materials, which often involve particular arrangements of more than three elements.

We have developed techniques to synthesize and characterize complete combinations of an alloy system using one or a few substrates. An example is shown below for the magnetic properties of a ternary system containing Co, Mn, and Ge, grown epitaxially on Ge (100) substrate. The result appeared on the cover of the April 2002 issue of MRS Bulletin and in a feature article in the same issue - "Continuous phase diagramming of epitaxial films" by Yoo & Tsui, page 316). From these measurements, ferromagnetic (F) and antimagnetic (AF) regions with high transition temperature and high spin polarization and paramagnetic (P) regions can be identified for the first time, and the interplay between structure, magnetism, and transport can be studied systematically. Fundamental processes that control epitaxial growth and spin polarization of these complex systems are being explored.