Experimental studies of noise in isotropic longitudinal CoCrTa/Cr thin-film media

The authors review some experimental studies of the intrinsic noise of isotropic high-coercivity longitudinal CoCrTa/Cr thin film media. Micromagnetic studies of the reverse DC erase maximum noise state and recorded transitions showed the presence of magnetic clusters and vortices. The transition length was found to be about four vortex diameters. The noise was found to decrease significantly at high substrate temperature due to a refinement of the magnetic microstructure which was not affected by the morphology of the Cr underlayer. In situ recording studies of the average spatial distribution of parallel and cross-track correlation lengths of reverse DC erase noise were shown to be in good relative agreement with micromagnetic studies. It is concluded that the intrinsic noise of CoCrTa/Cr is dominated by intergranular interactions which are probably controlled by segregation or stress-induced wall pinning instead of by physical isolation of grains