Scaling and dynamics of low-frequency hysteresis loops in ultrathin Co films on a Cu(001) surface

Abstract

The hysteresis loops of epitaxially grown ultrathin Co films on a Cu(001) surface with magnetic anisotropy were measured in situ at room temperature under a periodic external field by the surface magneto-optical Kerr-effect technique. A dynamic phase transition occurs at high frequencies. At very low frequencies, \ensuremath{\Omega}, a constant hysteresis loop area exists. We also observed power-law scaling of the loop area, A\ensuremath{\sim}${\mathit{H}}_{0}^{\mathrm{\ensuremath{\alpha}}}$${\mathrm{\ensuremath{\Omega}}}^{\mathrm{\ensuremath{\beta}}}$, for ${\mathit{H}}_{0}$>40 Oe and \ensuremath{\Omega}/2\ensuremath{\pi}90 Hz, with exponents \ensuremath{\alpha} and \ensuremath{\beta} each about 2/3. The observations are consistent with a mean-field Ising model.