Thermal stability in perpendicular recording media

Magnetic and structural properties of CoCrPt based perpendicular recording media required to achieve both high thermal stability and low-noise performance are discussed, based on experimental results obtained using a pulse magnetometer. Experimental and theoretical analysis reveal that for CoCrPt based media of 20nm thickness having the thermal stability factor K_uV/(kT)≈80, the maximum achievable value of the ratio of remanence coercivity to anisotropy field of grains, H_r/H_k is ∼0.35. Furthermore, in order to realize a large squareness M_r/M_s of nearly 1.0, which is required to resist the thermal agitation effect at low recording density, we find that the value of perpendicular magnetocrystalline anisotropy, K_u needed to be more than three times larger than 2πM_s². X-ray diffraction patterns suggested that the suppression of structural imperfections in the HCP structure, particularly in the initial growth layer, is the key issue to induce larger K_u value in the CoCrPt based media.