Magnetic characteristics of monodispersed Co/CoO cluster assemblies

The surface morphology of the (Fe1 − xCrx)0.09Cu0.91 films does not change significantly as x increases. No Fe or Cr granules form in the films because of the low deposition temperature and the non-equilibrium deposition procedure, suggesting that Fe and Cr atoms disperse in the Cu matrix. With increasing x, the lattice constant c and single cell volume decrease, but the lattice constants (a, b) first increase and latterly decrease. The films show spin-glass-like manner that looks like superparamagnetism at high temperatures and are ferromagnetic at low temperatures. The peak temperature of the zero-field-cooling curves decreases from 37 to 23 K as x increases from 0 to 0.25. Below the peak temperatures, the field-cooled magnetization decreases with decreasing temperature due to the antiferromagnetically coupling of the disordered spin-glass-like moments. The coercivity increases greatly below 50 K because of the pinning effect of the frozen spin-glass-like moments at low temperatures.