Domain wall dynamics and Barkhausen noise in ferromagnetic films/
The Barkhausen noise (BN) in soft magnetic systems can provide important information on the magnetization dynamics and on the domain wall (DW) motion. Especially for bulk materials there is a well established and consistent interpretation of the noise statistics, including statistical functions such as the distributions of Barkhausen jump sizes and durations, average size vs. duration and the power spectrum, which all follow power laws with exponents τ, α, 1/(σηz) and ν, respectively. For thin ferromagnetic films the BN properties are not so well understood due to several experimental difficulties, the insufficient amount of data, and to the complex morphology of the magnetic domains. In this work, we report BN results obtained with traditional inductive method in polycrystalline and amorphous ferromagnetic films in a wide range of thickness, between 20 and 1000 nm. In particular, we perform a wide statistical analysis of the noise, including the recently considered average avalanche shape, and considering theoretical predictions of several models for the DWs motion and images of the magnetic domain structure, we show that the BN statistical properties are strongly affected by the interplay of film thickness, related to the system dimensionality, and the structural character, associated to the range interactions governing the DWs dynamics.
Prof. Dr. Felipe Bohn – ECT/UFRN