Activation volume and correlation to media noise in high-density longitudinal recording media

Abstract

The activation volume (V,) and its correlation to media noise in high-density longitudinal recording media are investigated. Magnetization decay is observed to be non-linear with In(t) for the media studied, and the necessity for using a correct method for estimating a fluctuation field is emphasized. The activation volumes are shown to increase with decreasing reversing fields and the values of V, at low fields (of a few hundred Oe) are significantly higher than those at the coercivity. Thus, the collective behavior of the magnetic grains is influenced not only by the intergranular interactions but also by the stray fields. The media noise of different media is correlated to the V, values at low fields.

Improved grain isolation of Co/sub 80/Pt/sub 20/ films via grain boundary diffusion of Mn

“…The activation volume of magnetic reversal, has been shown to be correlated with the intergranular exchange coupling in the media and the media noise [9], [10]. Smaller that is close to the physical volume of the magnetic grains indicates that they are less exchange coupled, and the media normally will have smoother transitions and thus show lower noise.…”

Effect of thermal fluctuations on magnetization reversal of L10 FePt nanoparticles

“…Thus the thermal activation volume V ac can be expected to give some information on magnetization behaviour of the nanoparticles discussed above. Several methods can be used to calculate V ac [38,[54][55][56][57][58][59][60]. Here we adopted the method to determine V ac by measuring the viscosity coefficient and irreversible susceptibility [38,54].…”

Monte Carlo simulation of thermal activation volume in longitudinal hard-disk drives media

“…However, the field dependence of V ac obtained by using several methods is different from each other. [3][4][5][6] In a previous study we investigated thermal activation volume V ac through micromagnetic simulation by using the Langevin equation, and found that ͑1͒ V ac should be obtained by using irreversible magnetization; ͑2͒ a method without eliminating reversible magnetization leads to a wrong dependence of V ac * on the applied field. 6 However, it is to be noted that this calculation has been carried out at the thermal stability factor K ␤ (ϭK u V/kT) of 18.7 in order to solve the Langevin equation in reasonable computational time ͑where K u is the anisotropy constant, V is the volume of a grain, k is the Boltzmann constant, and T is the tempera-ture͒.…”