Domain Wall Creep in an Ising Ultrathin Magnetic Film

We have studied the motion of a magnetic domain wall (MDW) driven by a magnetic field H in a 2D ultrathin Pt/Co/Pt film showing perpendicular anisotropy and quenched disorder. MDW velocity measurements down to the so called creep regime show that the average energy barrier scales as $(1/H{)}^{\mu }$ with $\mu =0.24\mathrm{}\pm 0.04$ and that the correlation function along a MDW is governed by a wandering exponent $\zeta =0.69\mathrm{}\pm 0.07$, in very good agreement with theories giving $\mu =0.25\mathrm{}$ and $\zeta =2/3\mathrm{}$. This is the first direct measurement of the creep regime for a moving interface in a disordered medium.