Paramagnetic-ferromagnetic phase transition and magnetic properties of ultrathin CoFe/Cu(110) films

We present the results of a systematic investigation of the coverage-dependent magnetic response and anisotropy of ultrathin Co75Fe25/Cu(110) films using the magneto-optic Kerr effect. A paramagnetic-ferromagnetic phase transition is found to occur at a critical thickness d(c)=4.0 +/- 0.25 ML. In the vicinity of d(c), the paramagnetic susceptibility chi follows a power law with a critical exponent of gamma=2.385 +/- 0.069 in excellent agreement with the theoretical value for a perfect two-dimensional geometric percolation phase transition. At the very onset of ferromagnetic order, a mixture of cubic and uniaxial anisotropy was observed. (C) 2007 American Institute of Physics.