Micromagnetic modeling of low noise perpendicular media

The effect of magnetic anisotropy constants and inter-granular exchange coupling on properties of hcp CoCrX perpendicular media was studied by micromagnetic modeling. It was found that the second anisotropy constant K-2 reduces the energy barrier, coercivity H-C, saturation field H-S and, as a result, promotes writeability of the media for fixed anisotropy field H-K. H-C inversely decreases with the increase of K-2/K-1 ratio. Exchange coupling modifies a domain structure of the media in a virgin state and slope of hysteresis loop by reducing the coercivity and saturation field, and marginally increasing the nucleation field. Magnetic domains were found even in the decoupled media. The minimal domain size is about 2.5.d(G), where d(G) is an average grain size of the media. The domain size increases exponentially with the inter-granular exchange. The transition parameter and dc noise is reduced with increased exchange coupling. At a specific exchange coupling the dependence of the transition parameter on the exchange almost disappears, approaching a minimum value of d(G)/3. (C) 2002 American Institute of Physics.