Misfit Strain, Dislocations and Magnetism in Epitaxial Nano-Dots

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0105423O'HandleyNew, powerful ME-coefficient measurement techniques are used to study the effects of strain and dislocations in epitaxial magnetic nano-dots. The effects of limited lateral dimensions on strain relief and on ME effects are examined by using interferometric lithography to make highly-regular patterned arrays of magnetic dots and ovals having lateral feature sizes down to 25 nm and thickness from 2 to 20 nm. The program focuses on epitaxial Ni80 Fe20 and cobalt films on Cu-buffered Si (001), materials important for many magnetic thin film applications. The characterization of the film and dot arrays makes use of (a) synchrotron x-ray diffraction at BNL to determine strain, (b) torque magnetometry to characterize magnetic anisotropy, (c) vibrating sample magnetometry to determine saturation magnetization and Curie temperature, (d) differential capacitance measurements of first-order and second-order ME coupling coefficients, as well as (e) UHV and cryogenic magnetic force microscopy (in collaboration with the University of Basal), and scanning electron and transmission electron microscopy. Strain and ME coupling coefficient measurements on arrays at these small dimensions will provide important information for reliable processing of magnetic thin film devices. Further, the magnetic dots will mimic the behavior of grains in polycrystalline materials where grain boundaries provide some relief of intra-grain epitaxial misfit strain. %%%This study has excellent potential for advances in science with relevance to new technology in spintronics as well as magnetic random access memories.***