Magnetic Properties to Optimize the Effect in Perpendicular Recording Media

We calculated the optimal values of the first- and second-order uniaxial magnetic anisotropy energy terms, K_u1 and K_u2 , for thermal stability and writability in perpendicular media which use the K_u2 effect. The magnetic energy barrier DeltaE for the remanent state with demagnetizing field 4pilangM _srang was calculated for various K_u1 and K_u2 values, and we obtained the grain volume V_grain to satisfy DeltaEV_grain/kT=60 for thermal stability (k is the Boltzmann constant, and T the absolute temperature). Moreover, the switching field was calculated assuming a saturation field less than 16 kOe for good writability. The K_u2 term enhances the DeltaE in the remanent state of magnetization, without a notable increase in H_s. It is concluded that the best langM_s rang value to take advantage of the K_u2 effect is about 500emu/cm³, with K_u1=5times10⁶ erg/cm³ and K_u2=2.6times10⁶ erg/cm ³. The K_u2 term allows V_grain (and also the grain size) to be reduced by almost one-half, compared with a grain without a K_u2 term, while simultaneously achieving good thermal stability and writability