The influence of anneal on the structural and magnetic properties of the electrodeposited thin-film alloy Cu94Co6

Magnetic measurements have been made in the temperature range 2 to 300 K and in fields up to 5 T on the electrodeposited, thin-film alloy Cu94Co6 The unannealed alloy, which magnetic measurements suggest consists of face-centred cubic (f.c.c.) Co-rich particles in an f.c.c. Cu-rich matrix, exhibits superparamagnetism and has a maximum blocking temperature, as determined from hysteresis loops, of 55+/-5 K. Low-field susceptibility measurements give an interaction energy of 1.7 x 10(-3) eV. Samples have been annealed at temperatures up to 600 degrees C. The effect of anneal is to produce a strong increase of remanence and maximum blocking temperature, which corresponds to a growth in particle size, together with an increase in the interaction energy. After the final anneal to 600 degrees C, the blocking temperature is well above 300 K and the sample shows ferromagnetic behaviour. Detailed electron microscopy measurements have also been made in order to determine the structure of the film and its modification on anneal.