Influence of the structure defects on the magnetic properties of the FePt/Fe bilayer

Thin magnetic multilayered films containing FePt have attracted a lot of attention recently due to their possible usage in ultra-high density magnetic storage. Although structure defects play a dramatic role in the magnetization process and influence magnetic properties in general this dependence have not been studied thoroughly. The main aim of this work was to perform theoretical investigation of the magnetic properties of FePt and Fe/FePt thin films with high coercivity with respect to the structure defects such as anisotropy constant, magnetization saturation, exchange constant fluctuations, and easy axis deviation. For selected defect patterns, the coercive field dependence on layer thicknesses was analysed. Numerical study of the bilayer with hard magnetic layer having the planar anisotropy was carried on using micromagnetic calculations. Values of layers thickness have been found optimal for perspective applications, the dependence of the hysteresis loop shape upon the magnetization process has been shown and analysed.