Structure and magnetic properties of 300-nm-thick FePt films with Hf underlayer

Structure, microstructure, magnetic properties of 300-nm-thick FePt films with 10-nm-thick Hf under layer have been studied. The experimental results showed that the very thin Hf underlayer could promote the ordering at reduced temperatures by facilitating the nucleation of the order phase, leading to refined grain size and magnetic domain size. Therefore, the permanent magnetic properties of FePt films were enhanced. (BH)(max) and H-c of FePt films were greatly enhanced from 5.0-21.0 MGOe and 1.4-11.0 kOe for single layer to 10.2-23.6 MGOe and 4.5-13.2 kOe for Hf-underlayered films annealed in T-a region of 400-600 degrees C, respectively. Nevertheless, the severe interdiffusion between the Hf and FePt layers at T-a=800 degrees C resulted in the decreased S, coarsened surface morphology, grain and magnetic domain sizes, and therefore the slightly decreased (BH)(max) to 18.0 MGOe. (C) 2016 Elsevier Ltd. All rights reserved.