Roughness Exponent of Domain Interface in CoFe/Pt Multilayer Films

Critical scaling behavior of magnetic domain interfaces is experimentally investigated in Pt/CoFe/Pt single-layer film (type I) and (CoFe/Pt)₄ multilayer film (type II). Even though both samples exhibit domain wall propagation with rare nucleation, the domain interface profile is found to be very contrasting. Typical overhanging interfaces, in contrast to smooth interfaces in type I film, are observed in type II film. Both types of the interface profiles obey power laws. In log-log scaling plot of the roughness with respect to the interface segment length, the slopes, i.e., the scaling exponents, are estimated to be 0.66 plusmn 0.02 and 0.98 plusmn 0.03 for type I and II films, respectively. These values of the scaling exponents correspond to two distinct criticality classes of the self-affine and self-similar regimes in random-field Ising model, respectively.