Magnetic susceptibility determination of the relaxation time for domain-wall motion in perpendicularly magnetized, ultrathin films

The temperature dependence of the magnetic relaxation time τ(T) is investigated in perpendicularly magnetized, ultrathin Fe/2 monolayer Ni/W(110) films by magnetic susceptibility measurements. Complex magnetic susceptibilities χ(T)=χ′(T)+iχ″(T) were measured by the polar Kerr effect as a function of temperature T. In all cases, χ′(T) and χ″(T) have broad peaks that are not obviously related to the Curie temperature TC. An experimental …