The influence of oxygen pressure on the crystallographic structure and magnetic properties of BaM films on Al_2O_3(0001) substrate

摘要

In this work, hexagonal barium ferrite thin films have been deposited on Al_2O_3(0001) substrates by pulsed laser deposition. The influence of oxygen pressure on the crystallographic structure and magnetic properties of BaM films has been studied. X-ray diffraction theta-2theta reveals the films have a good c-axis orientation perpendicular to the film plane under low oxygen pressure. It is also observed from scanning electron microscope that grain shape in the film surface is changed from platelets into elongated acicular with the increase of oxygen pressure. Magnetic hysteresis loops show the saturation magnetization and remanence of BaM films are greatly depended on the oxygen pressure. They are initially increased to a maximum value, then drastic decreased with increase of oxygen pressure. Consequently, films deposited at 0.08Pa have the highest saturation magnetization of 3900 Gs and remanence ratio of 74.5% which are comparable with the theoretical value of BaM bulk.