Study On High Frequency Magnetic Properties And Core Loss Of Metallic Soft Magnetic Composites With Easy-plane Structures

With the development of new energy industries,power electronics devices are required to be able to work with a higher efficiency,higher energy density and more miniaturized state.The emergence of wide-bandgap semiconductors offers the possibility of developing such high-performance power electronics devices.However,there is no soft magnetic material that can fully unlock the potential of wide-bandgap semiconductors.Therefore,the development of soft magnetic materials that can operate effectively at higher frequencies is an inevitable topic for the development and deployment of new energy industries.In this paper,we developed four easy-plane soft magnetic composites(SMCs)operating at different frequency bands,including Fe Si Al,Fe Ni Mo,Fe Ni and carbonyl iron,and investigated the high frequency magnetization processes and core loss characteristics in comparison with the respective non-easy-plane SMCs.Based on the separated and fitted loss parameters,we inverted the core loss of the SMCs at higher frequency bands and estimated the performance factor(PF)of the SMCs over the entire operating frequency range.The relaxation frequency of the easy-plane Fe Si Al composite reaches 1 MHz,and the initial permeability is 200.The high frequency magnetization process contains domain wall motion and spin rotation mechanisms.The total core loss are 55 and 296 k W/m~3 at 500 k Hz,10 and 20 m T,respectively.The loss separation results show that the hysteresis loss is the main loss component up to 500 k Hz,and the excess loss becomes the dominate component at higher frequencies.The eddy current loss of the composite is effectively suppressed due to the surface insulating cladding treatment and the ultra-thin thickness of the easy-plane Fe Si Al magnetic powder particles.In addition,the PF of the composite at 500 k W/m~3 reaches 18 T·k Hz.The relaxation frequency of the easy-plane Fe Ni Mo composite is higher than Fe Si Al,reaching nearly 10 MHz,and the initial permeability is 82.Compared with the non-easy-plane Fe Ni Mo composite,both the initial permeability and relaxation frequency of easy-plane Fe Ni Mo composite are significantly improved.The hysteresis and eddy current losses increase due to the increased anisotropy of the easy-plane magnetic powder particles and the agglomeration between the particles,resulting that the core loss at 500 k Hz and 16 m T increased from 624 to 964 k W/m~3.After annealing and surface passivating,the hysteresis loss and eddy current loss are effectively suppressed,the total core loss at 500 k Hz and 16 m T reduces to 445 k W/m~3.Even so,the total core loss of the easy-plane Fe Ni Mo composite is still high,resulting in a lower PF of 15 T·k Hz at 500 k W/m~3,which is significantly lower than that of the easy-plane Fe Si Al composite and current commercial soft magnetic ferrites.The initial permeability of the easy-plane Fe Ni composite is 38,and the permeability remains constant with frequency until 30 MHz.The core loss is more linear with increasing frequency in the easy-plane composite compared to the non-easy-plane composite,and thus,the core loss is lower at high frequencies,decreasing from 929 to 621 k W/m~3 at 500 k Hz and 16 m T.The loss separation results show that the eddy current and excess loss are effectively suppressed,and the hysteresis loss dominates in the easy-plane composite,instead of the dominate excess loss in the non-easy-plane composite.As a result,the PF of the easy-plane Fe Ni composite reaches 30 T·k Hz at 20 MHz.In addition,the initial permeability of the easy-plane Fe Ni composite prepared by lamination reaches48,and the core loss at 500 k Hz and 16 m T is reduced to 262 k W/m~3.However,due to the reduction of the relaxation frequency,the excess loss percentage increases,the core loss at high frequencies increases,and thus,the performance factor is relatively reduced.The high relaxation advantage of easy-plane Fe Ni composite mainly comes from in-plane anisotropic field,which leads to the high hysteresis loss.In order to reduce the hysteresis loss,the easy-plane carbonyl iron composite were prepared.The permeability spectrum of the easy-plane carbonyl iron composite is very similar to the easy-plane Fe Ni composite,with an initial permeability of 36 and an relaxation frequency of 30 MHz.The difference is that the high operating frequency of the easy-plane carbonyl iron composite mainly comes from the out-of-plane anisotropic field.Due to this,the hysteresis loss of the easy-plane carbonyl iron composite is effectively reduced under high frequencies magnetization without increasing the excess loss,and thus,the total core loss,which is 361 k W/m~3 at 500 k Hz and 16 m T,is the lowest under the all of prepared easy-plane composites.In addition,the PF of easy-plane carbonyl iron comopsite reach 40T·k Hz at 40 MHz,which is the highest level among all the prepared composites,and is also high among the soft magnetic composites reported so far,also is a good reference for the development of SMCs for next-generation power electronics devices.In general,easy-plane composites have obvious advantages in terms of permeability performance and core losses compared to non-easy-plane composites.Therefore,the use of soft magnetic composites with easy-plane structures as core materials should be a very effective research direction for future ferromagnetic metal composites to unlock the potential of wide bandgap semiconductor and develop the next generation of high frequency and miniaturized power electronic devices.