Microstructure and electron transport properties of AuxCo1 − x nano-alloys embedded in polyacrylonitrile thin films

Abstract

Au_xCo_1 − x nano-alloys with a diameter below 10 nm were fabricated via a vacuum co-evaporation method. The composition dependence and the effect of heat-treatment on the microstructure of the Au_xCo_1 − x nano-alloys were investigated by means of electron diffraction analysis. The lattice constant of fcc Au_xCo_1 − x nano-alloys varied with the composition and heat-treatment. The results revealed that as-deposited Au_xCo_1 − x nano-alloys were in a thermodynamically metastable state, and the following heat-treatment led to their equilibrium state. Furthermore, phase transition from fcc solid solution to L1₀-type ordered face-centered tetragonal (fct)-structure partially took place during heat-treatment. The temperature and magnetic field dependences of electrical resistivity were investigated for polyacrylonitrile (PAN) thin films embedded with Au_xCo_1 − x nano-alloys, and a TMR value of 80% was obtained at room temperature under appropriate conditions.