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

The temperature dependence of the magnetic relaxation time tau(T) is invest igated in perpendicularly magnetized, ultrathin Fe/2 monolayer Ni/W(1 1 0) films by magnetic susceptibility measurements. Complex magnetic susceptibil ities chi(T) = chi(T) + i chi "(T) were measured by the polar Kerr effect a s a function of temperature T. In all cases, chi'(T) and chi "( T) have bro ad peaks that are not obviously related to the Curie temperature T-c. An ex perimental relaxation time tau(T) is determined from the ratio chi "(T)/chi '(T). The results support previous arguments that the susceptibility arises from domain-wall motion. (C) 1999 Elsevier Science B.V. All rights reserve d.