First Principles Study Of Magnetism And Damping Property For Ferromagnetic Damping Alloys

Magnetic damping alloys have been commonly utilized in the territory of modern industry due to its high damping performance, corrosion resistance, wide temperature range etc. The Fe-Cr-Al alloy series have excellent mechanical performance and is immune to be corroded. So a lot of scientists focus on the research of ferromagnetic damping alloys. So far, there are rare on theoretical calculation studies about Fe-Cr-Al alloy series. Correspondingly, a giant amount of research findings are from real experimental method. By using the latest materials scientific computing software WIEN2 K, this thesis successfully performed the research on the magnetic properties of Fe-Cr-Al alloys, and analyzes its relationship with damping performance.This thesis firstly explain the basic characterization and the newest research status of damping alloys.Then starting from the general idea of first principles, we use density functional theory to introduce the evidence of the theoretical calculation and give the work flow of WIEN2 K software. Major influence factor of damping property are derived by theory. We find that the relationship between magnetic damping performance and the ratio of magnetocrystalline anisotropy energy and the total magnetic moment is reversely proportional and is verified by experiments. Then based on first principles and density functional theory, we calculated the magnetic parameters of Fe₂ CrAl alloy by using WIEN2 K software. Through summarizing and analyzing these magnetic parameters, we found that the Er, Pm, Si and Tb elements can improve the damping performance of Fe₂ CrAl alloy, and damping performance gradually improve as above sequence.This thesis also deeply studied the damping mechanism of FeCrAlSi and FeCrAlTb alloys that have best damping performance in the four kinds of alloy（Er, Pm, Si and Tb）. Through the research, we found that p-d hybridization exists between Si-p and Fe-deg, Cr-deg, Cr-dt2 g orbital, which indirectly effects strongly d-d orbital hybridization effect between Fe and Cr atoms that makes anti-bonding state density of Fe and Cr atoms move to low energy region and produce two hybrid peaks in Fermi level. These varitions precisely interpret why the damping performance of Fe₂ CrAl is improved after doping Si. After doping Tb atom, alloy added a high states density and local Tb-f orbit, which increases the total states density of spin up on the left of the energy zero.In addition, f-d hybridization exists between Tb-f and Fe-d, Cr-d orbital, which makes the distribution of state density of Fe and Cr atoms become more discrete. These changes in state density and orbital hybridization resulted in the change of damping performance. Finally, we adopt the approach of changing the atomic positions in original cell to further boost the FeCrAlSi and FeCrAlTb alloy damping performance.Through theoretical analysis and experimental results, the preposed thesis got the relationship between damping performance and magnetism, and this conclusion can guide the future study of ferromagnetic damping alloy. In addition, using the method of theoretical calculation to get high damping ferromagnetic alloy, researcher can save more time and cost of experiment.