FIELD-DEPENDENT RESONANCE FREQUENCY OF HYSTERESIS LOOPS IN A FEW MONOLAYER THICK CO CU(001) FILMS/

Dynamic responses of magnetic hysteresis loops in a few monolayer (ML) thick Co/Cu(001) films were studied using surface magneto-optic Kerr effect (SMOKE). For a fixed external field strength H-0, the hysteresi s loop area increases as a function of frequency with a power law and reaches a maximum at a resonance frequency Omega(0). This Omega(0) dep ends on the external periodic field strength as well as the thickness and roughness of the films. The thickness and roughness parameters wer e measured quantitatively using high-resolution low-energy electron di ffraction. For a fixed film thickness, the Omega(0) in the low field r egion is highly dependent on H-0, which is consistent with the predict ion from the mean field model. For two Co films with an equivalent thi ckness but different degrees of film roughness, the resonance frequenc y Omega(0) is lower for the rougher films in all the field strengths s tudied. For a fixed field strength, the value of Omega(0) decreases as Co film roughness increases in a few ML regime. The roughness depende ncy in Omega(0) indicates that the slowing down in the magnetization r eversal process is due to the increased film roughness. (C) 1996 Ameri can Institute of Physics.