Magnetic Properties of Hexagonal Barium Ferrite Films on Pt(111)/Al2O3(0001) Substrate Based on Optimized Thickness of Pt

Abstract

In this study, hexagonal barium ferrite thin films have been deposited on Pt(111)/Al2O3(0001) substrates by pulsed laser deposition. The thickness of Pt dependence of crystallographic structure and magnetic properties has been studied. X-ray diffraction θ-2θ reveals the films have a good c-axis orientation perpendicular to the film plane. Furthermore, pole figure analysis discovers that the crystallinity of films is greatly improved by Pt buffer layer and the highest degree of orientation is prepared at 20-nm-thick Pt. It is also observed from scanning electron microscope and atomic force microscopy that the BaM film with 20-nm-thick Pt is formed as hexagonal shaped and has smaller than 2 nm of roughness. Magnetic hysteresis loops show the saturation magnetization ( ${\rm{M}}_{{\rm{s}}}$ ), coercivity ( ${\rm{H}}_{{\rm{c}}}$ ), and uniaxial anisotropy field ( ${\rm{H}}_{{\rm{k}}}$ ) are greatly depended on the thickness of Pt buffer layer. Consequently, films with 20-nm Pt buffer layer have the highest ${\rm{M}}_{{\rm{s}}}$ of ${\rm{358\,emu/ cm}}^{3}$ and ${\rm{H}}_{{\rm{k}}}$ of 16.7 kOe which are comparable with the theoretical value of BaM bulk.