Phase separation in Cu90Co10 alloys processed by twin roller melt spinning

HENRY NÚÑEZ COAVAS; GABRIELA POZO LÓPEZ; SILVIA E. URRETA ; LUIS M. FABIETTI

Buenos Aires

Congreso; VIII Reunión Anual de la Asociación Argentina de Cristalografía; 2012

Cu1-xCox alloys processed by single roller melt spinning and further heat treated in the range 400–973 K exhibit giant magnetoresistance (GMR). In the as-quenched samples Co is present in two main structural components small, irregular, strained Co particles and within a spinodal like composition modulated CoCu alloy; this concentration profile splits the alloy in two parts with distinctly different properties. One part is a ferromagnetic soft alloy and the other one is a paramagnetic alloy with a blocking temperature below 4.2 K. This structure has a 40-60nm modulation period and develops along the crystalline directions of each grain.  In this work are studied the phase separation and the resulting nanostructures in twin rolled melt-spun Cu90Co10 ribbons, both, in the as cast state and after 1h at 823K. This solidification technique allows to impose a symmetric heat extraction geometry leading to more homogeneous nanostructures; with this procedure Cu90Co10 alloys exhibit GMR effects even in the as cast condition [3].  The microstructures obtained at tangential wheel speeds between 5 and 40 m/s, are characterized using x ray diffraction techniques and magnetic measurements