Magnetic phases in nanogranular Co–Cu structures

Abstract CoCu nanogranular materials with Co concentration of 5, 9, and 15 at% were produced by annealing the starting melt-spun ribbons at 450°C for 1 h. Their magnetization curves were quantitatively analyzed for the amount of superparamagnetic and ferromagnetic phases in the temperature range of 5–300 K. For the two lower concentrations the majority of particles became already superparamagnetic at these temperatures. The temperature dependence of the AC susceptibility indicated the presence of antiferromagnetic type interactions among the particles.