Exchange coupling strength in synthetic ferrimagnetic media

The antiferromagnetic exchange coupling strength (H/sub ex/) between two CoCrPtB magnetic layers in bilayer synthetic ferrimagnetic media (SFM) is investigated. H/sub ex/ is found to be inversely proportional to the thickness and magnetization of the initial magnetic layer (L1). H/sub ex/ also shows a decrease with increasing temperature. An exchange coupling strength of J/spl ap/0.05 erg/cm/sup 2/ was obtained from H/sub ex/. For further improvement of thermal stability at higher recording densities, the thickness or magnetic anisotropy of L1 may be increased. On the other hand, for an effective SFM, the coercivity of L1 must be lower than H/sub ex/. Therefore, a large H/sub ex/ is critical for better thermal stabilization.