Thermal stability of information storage tapes prepared from very fine metal particles

Abstract

The magnetic viscosity coefficient (Sv), the normalized magnetization decay for logarithmic time [ΔM/(Mrlogt)], the thermal stability factor, and the anisotropy field (HA) distribution were studied for metal particulate (MP) tapes prepared from acicular very fine Fe-Co particles as a function of average crystallite size (D110). D110 values of Fe-Co particles varied from 10.6 to 14.3nm. Sv increased as D110 decreased. In MP tape with a D110 value of 10.6nm, a small proportion of particles had low HA values. In the reverse field of 0.5kOe, the values of ΔM/(Mrlogt) at 350K and the thermal stability factor for MP tape with D110 value of 10.6nm were approximately 0.39%/decade (∼3.1%/3 years) and 109, respectively. The result suggests that the critical value of D110 could be approximately 9nm for MP tapes prepared from ultra-fine Fe-Co particles (aspect ratio ∼3.5) with the average HA of approximately 3.4kOe.