Transient Behavior of the Dynamically Ordered Phase in Uniaxial Cobalt Films

We study the time dependent magnetic behavior of uniaxial cobalt films in the vicinity of the dynamic phase transition (DPT) as a function of the period P and bias H-b of an oscillating magnetic field. In addition to the DPT at a critical period P-c, we observe the occurrence of transient behavior for P < P-c. Our data can be consistently explained by the existence of a phase line at H-b = 0 for P < P-c, which causes a first order phase transition in between two antiparallel dynamic order states, thus indicating far-reaching similarities of the DPT to equilibrium phase transitions in ferromagnets.