Grain geometry induced reversal behaviour alteration

Abstract

According to the experimental investigations, it is reported that the magnetic switching field is varied by the stacking orders in the recording media composed of stacked structure. The lattice distortion due to the lattice mismatch between two layers has been suggested as an origin of the difference; however, it has not been clearly explained up to now. In this paper we studied the possibility of the contribution of the convex surfaces in recording media. The convex surfaces vary the ratio between local magnetic anisotropy and intergranular exchange coupling strength that influences the magnetic behaviours of the stacked granular structure. An analytic model including the local geometric inequivalency is presented. From the analytic equations, it is found that the uniaxial anisotropy of the concave bottom layer can be overcome more easily than other parts, with the assistance of the intergranular exchange. Consequently, the harder bottom layer can be reversed earlier than the softer top layer, under some appropriate conditions. The analytic results are proved by finite element micromagnetic simulations.

Role of interface morphology in the exchange-spring behavior of FePt/Fe perpendicular bilayers

“…On the other hand, the importance of extrinsic media characteristics, like grain shape and hard/soft interface details, has rarely been looked at in depth in either theoretical or experimental works [16,17]. Model systems with controlled extrinsic properties could be fruitfully exploited to both understand the limits of real ECC systems and improve the functional properties, as, for instance, in graded anisotropy or ledge media.…”