Research On Tailoring Magnetic Properties Of Magnetic Films

With the development of technology, all kinds of electronic equipments have come into people’s life and bring great convenience. But at the same time, electromagnetic radiation pollution is becoming more and more serious. Besides, in military area, there is a huge demand for stealth technology. The development of electromagnetic shielding and stealth technology involves a number of military industry and civil technology areas and is in urgent need of effective materials and technologies in which soft magnetic materials play an important role. In addition to electromagnetic shielding and microwave absorption, there is also a great need of soft magnetic materials in all kinds of electronic components. Soft magnetic materials are essential in many applications and technologies, from traditional transformer and inductor to modern technologies such as near field communication and wireless charging. People are paying more attention to the study of soft magnetic materials to improve their performance.Since the 21st century, miniaturization, integration and high frequency application become more important in electronic and information industry. This is a great opportunity for soft magnetic films and research on soft magnetic films have attracted more and more attention. Tuning the magnetic properties of soft magnetic films is very important to meet different demands. In this respect, theoretical basis are quite rich, but a lot of things still worth exploring. Changing the composition, thickness and preparation conditions of magnetic films are typical ways to manipulate the magnetic properties of them. Besides, using an underlayer is also an effective method to tune the magnetic properties. Our main work is as follows:1. We introduce a new method to modify underlayers by an argon ion etching technology. In our experiment, we used different ion etching conditions to etch substrates with underlayers and observed the change of surface roughness by AFM. Then FeCoB films were deposited on the treated substrates by magnetron sputtering. All the films were treated with magnetic field annealing in order to remove the internal stress and to induce an in-plane uniaxial magnetic anisotropy. Surface roughness of underlayers, as well as soft magnetic properties of post-deposited FeCoB films can be improved by applying a proper ion etching process, which means the magnetic coercivity is affected by interfacial roughness. Damping linewidth of magnetic films is also found to be related to the interfacial roughness from the microwave magnetic spectrum and it is because modified underlayers can reduce the influence of two-magnon scattering effect. Results show that interface modification can effectively tailor magnetic properties of magnetic films.2. The sandwich structure of FeCoB/MgO/FeCoB is extremely popular in magnetic tunneling junctions (MTJ) nowadays. We found interesting coupling effect between the two magnetic films when they become thicker than traditional MTJs in our experiment. So we are trying to discuss the possibility of tuning the overall magnetic properties of the structure by coherent tunneling. We are still proceeding the experiment and it is meaningful to explain the coupling effect between the magnetic films.