Significant Deterioration Of Energy Products Due To Easy Axis Deviations In Hard/soft Bilayer

Abstract:Nanocomposite hard/soft magnet is a new type of magnetic material, attracted much attention in research and application with the development of science and technology. In this paper, quasi-analytical method (1D) and numerical method (3D) are adopted to investigate the hysteresis loops of hard/soft bilayer with different easy axis orientation. The remanence, coercivity and energy products for the system with various β are discussed. The main research results are as follows:(1) The easy axis is parallel to the film:calculated hysteresis loops for Nd2Fe14B/a-Fe with different hard layer thickness while β= 10°and 30°.Analyzed the magnetic properties for the system, we find that there is no obvious nucleation while a tilting of the easy axis exist. All magnetizations of the system orient at the easy axis directions, that θh=θs=θ0=β, and θh、θs and θ0 increase as the applied field decreases. As β increases, remanence and coercivity of the system decrease, leading to energy product decreases. Compare the results obtained from 1D and 3D method, we can find that the remanence, coercivity, energy product and pinning fields are very similar.(2) The easy axis is perpendicular to the film:a clear nucleation occurs when β= 0°. Because of the easy axis is not collinear with the applied field, the magnetization cannot arrive at the saturation state, only can approach the saturation state, so there is no clear nucleation. When the applied field equal to 0, all θh、θs and θ0 cannot orient at the easy axis directions because of the demagnetization energy. All θh、θs and θ0 increase as the applied field decreases. The gaps between θh and θs,θh and θ0 increase as applied field decreases, which arrive maximum at pinning point. As β increases, remanence decreases and the pinning field increases, coercivity increases in the first and then decreases.