Temperature dependence of the magnetization reversal of thin-film longitudinal magnetic recording media

As longitudinal magnetic recording media approach the superparamagnetic limit, temperature-dependent effects are becoming ever more important. This work reports an unexpected temperature dependence for the Sharrock stability parameter S typically given as K/sub u/V/k/sub B/T, where K/sub u/ is the uniaxial anisotropy, V the switching volume, k/sub B/ is Boltzmann's constant, and T the temperature. Temperature-dependent vibrating sample magnetometer measurements were made of the saturation and remanent magnetization M/sub s/ and M/sub r/, remanent coercivity H/sub cr/, and K/sub u/. The Sharrock equation was used to calculate S, and the time-independent switching field H/sub o/ of representative longitudinal recording media. Instead of the product Sk/sub B/T decreasing proportionally to K/sub u/ or H/sub o/ with increasing temperature as initially expected, we find Sk/sub B/T decreases at approximately half this rate.