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

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, {Ω}, a constant hysteresis loop area exists. We also observed power-law scaling of the loop area, A{~}H₀^α{{{Ω}}}^{{{β}}}$, for ${H}₀$>40 Oe and {Ω}/2{π}90 Hz, with exponents {α} and {β} each about 2/3. The observations are consistent with a mean-field Ising model.