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

AuxCo1 (-) (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 AuxCo1 (-) (x) nano-alloys were investigated by means of electron diffraction analysis. The lattice constant of fee AuxCo1 (-) (x) nano-alloys varied with the composition and heat-treatment. The results revealed that as-deposited AuxCo1 (-) (x) nano-alloys were in a thermodynamically metastable state, and the following heat-treatment led to their equilibrium state. Furthermore, phase transition from fee solid solution to Ll(0)-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 AuxCo1 (-) (x) nano-alloys, and a TMR value of 80% was obtained at room temperature under appropriate conditions.