Magnetic properties of nanogranular CoxCu1-x structures

CoCu nanogranular specimens with Co concentration of 5, 9 and 15 at.% were produced by annealing the parent melt-spun ribbon at 450 and 600 degrees C for 1 h. Their magnetization curves were quantitatively analyzed for the amount of superparamagnetic and ferromagnetic phases in the temperature of measurement ranging from 5 to 300 K. For the two lower concentrations and lower temperature of annealing, the great part of particles became already superparamagnetic within this temperature range. The temperature dependencies of both, magnetization measured in ZFC and FC regimes and initial AC susceptibility, indicated the presence of mictomagnetic state in the studied specimens at low temperatures. Analyses of the latter dependencies pointed to antiferromagnetic interactions existing between particles. Temperature dependencies of the coercivity for samples annealed at 600 degrees C were consistent with those published in the literature, whereas these dependencies for samples annealed at 450 degrees C indicated non-monotonous shape possibly reflecting interactions among superparamagnetic particles. (c) 2004 Elsevier B.V. All rights reserved.