Effect of Thermal Agitation on the Magnetic Properties of CoCrTa Perpendicular Recording Media

The effect of thermal agitation of magnetization on the magnetic properties of CoCrTa/Ti perpendicular media was studied by using a pulse magnetometer. The values of the “intrinsic” remanence coercivity H0, obtained by subtracting the thermal agitation of magnetization, are several times larger than those of the remanence coercivity Hr measured experimentally at a field sweep rate of ∼5 Oe/s. The value of H0 gradually approaches Hk as the CoCrTa thickness decreases, and shows values larger than 90 % of Hk at thicknesses of less than 20 nm. This indicates the potential of perpendicular media to achieve Hr values equal to Hk. The activation volume gradually decreases as the thickness decreases, and is nearly the same as the mean grain volume at thicknesses of less than 30 nm. This suggests that magnetization reversal within the grains is uniform at thicknesses of less than 30 nm, even though the grains have an elongated shape (30 nm x 9.52 nm2 at 30 nm thickness, for instance). This will be another advantage of perpendicular media in resisting thermal agitation of magnetization.