Demonstration of the thermal stability advantage of advanced exchange coupled composite media

We systematically vary the strength of the vertical interlayer exchange coupling (VIEC) between the magnetic layers (MLs) of an advanced exchange coupled composite media and experimentally investigate, through magnetic viscosity and dynamic coercivity measurements, the impact on the thermal stability. The strength of the VIEC is controlled through exchange coupling layers of varied thicknesses, whereas MLs are unchanged. We estimate the thermal energy barrier ΔEo as a function of the VIEC within the standard Arrhenius-Neel relaxation and Sharrock formalisms and characterize the effect of the VIEC on the degree of incoherency in the grain reversal mechanism. The analysis shows that while ΔEo drops for weaker VIEC, the ratio of ΔEo to MsHo energy per activation volume is maintained near 2 and weakly optimizes for intermediate VIEC.