Effects of soft layer softness on the magnetic properties of perpendicular exchange-coupled nanocomposite films

The anisotropy of the soft layer in the Co100−xPtx/Co71Pt29 (x=0, 7 and 17) perpendicular exchange-coupled composite (ECC) films was varied by changing the Pt content. The effects of soft layer softness (thickness and anisotropy) on the coercivity and magnetization reversal mechanisms of ECC were studied. Results showed that both remanence ratio (Mr/Ms) and coercivity of the ECC films reduced with an increase in soft layer thickness. However, the rate of coercivity reduction reduced when soft layer anisotropy was increased simultaneously. This was confirmed by the following facts. For the ECC with Co soft layer, the magnetization reversal mechanism within the ECC grains changed from coherent rotation to domain wall motion when soft layer thickness was changed from 2 to 15 nm. The impact of soft layer thickness on the magnetization reversals of the ECC grains reduced with an increase in soft layer anisotropy. On the other hand, the change of soft layer easy axis direction could possibly change the reversal mechanism of the ECC grains. The above experimental results showed that the coercivity of ECC film was controlled by the reversal mechanism inside the ECC grains.

► Both remanence ratio and coercivity of the ECC films reduced with an increase in soft layer thickness.
► Reduction of coercivity was confirmed by the facts for the ECC with Co soft layer.
► Coercivity of ECC film was controlled by the reversal mechanism inside the ECC grains.