Magnetic Dipole Interaction In FINEMET Composite Structure Ribbons

The variation of magnetic properties of soft magnetic materials can be induced by the adjacent materials.It is very necessary to investigate the variation of nanocrystalline(FINEMET)ribbons induced by the surrounding materials.The magnetic dipole interaction is one of the important physical mechanisms that regulate the intrinsic properties of magnetic materials.Therefore,it is significant to study the magnetic dipole interaction and its influence on the magnetic properties of soft magnetic materials.In this thesis,based on the magnetic dipole interaction,we construct a theoretical model and analyze the relationship between the geometric factor(K)and the magnetic dipole interaction.Besides,it has been proved that the giant magneto-impedance effect(GMI)and the hysteresis loop are useful method for investigation of magnetic dipole interaction.Furthermore,single-layer,double-layer and three-layer nanocrystalline composite structure ribbons were designed and prepared,and the effects of the magnetic dipole interaction on the magnetic anisotropy field(H_k),peak position field(H_p),plateau end field(H_end),coercivity(H_c),susceptibility(?),sensitivity(?)and magnetic properties of the composite structure ribbon are discussed.The framework of this paper is as follows:Chapter 1 introduces the nanocrystalline soft magnetic materials and composite structures,magnetic interactions and giant magneto-impedance effects.The second chapter describes the material preparation and characterization technology.A variety of nanocrystalline composite structure ribbons were prepared by single-roller melt quenching,chemical vapor deposition(CVD),electroless plating,magnetron sputtering and a combination of heat treatment and hydrogen annealing processes.Chapter 3 uses nanocrystalline ribbons with transverse magnetic structures to construct the magnetic dipole interaction model,and it was analyzed the magnetic dipole interaction between the probe nanocrystalline ribbon and the dipole nanocrystalline ribbons.The relationship between geometric factor(K)and magnetic dipole interaction was discussed.The fourth chapter is the study of the magnetic properties of the nanocrystalline/magnetic layer(FINEMET/Fe₁₀Co₉₀)composite ribbons.The peak position field,magnetic anisotropy field,magnetic susceptibility,coercivity and the thickness of the Fe₁₀Co₉₀layer of the composite ribbon are analyzed.The internal physical mechanism is reasonably explained from the perspective of the magnetic dipole interaction.Chapter5 is the study of the magnetic properties of nanocrystalline/graphene/magnetic layer composite structure(FINEMET/G/Fe₁₀Co₉₀)ribbons.By changing the number of graphene(G)layers and the thickness of Fe₁₀Co₉₀layers to study the influence of geometric factor on the magnetic properties of nanocrystalline composite ribbons.At the same time,the co-competition model of magnetic dipole interaction,electromagnetic interaction and stress were used to explain the variation of the peak position field,magnetic anisotropy field,and coercive force.The last chapter is the summary and prospect for the future study.The main research contents and conclusions of this paper are as follows:1.Magnetic dipole interaction in FINEMET ribbons(1)When multiple dipole nanocrystalline ribbons are arranged in parallel around the reference probe nanocrystalline ribbon,the peak position field(H_p)and plateau end field(H_end)of the magneto-impedance curve show a linear increase trend with the increase of the number of dipole ribbons.This is due to the fact that the magnetic dipole interaction is linearly superimposed on the peak position field and the plateau end field of the reference probe nanocrystalline ribbon.(2)When the driving frequency of the reference probe ribbon changes in the range of200 k Hz to 80 MHz,the plateau end field(H_end)of the reference probe ribbon does not change significantly,but the peak position field(H_p)of the reference probe ribbon increases sharply after at a frequency of 40 MHz.This is due to the combined effects of compensation field(H_com),eddy current loss,and rotational damping.2.Magnetic dipole interaction in FINEMET/Fe₁₀Co₉₀composite structure(1)The different thicknesses of Fe₁₀Co₉₀magnetic layers were deposited on the smooth surface of FINEMET ribbons to form FINEMET(smooth surface)/Fe₁₀Co₉₀composite ribbons.When the thickness of the Fe₁₀Co₉₀magnetic layer changes from10 nm to 60 nm,the magnetic anisotropy field of the composite structure ribbons shows a trend of first decreasing and then increasing.This is related to the competition relationship of magnetic dipole interaction and stress between the nanocrystalline ribbon and the Fe₁₀Co₉₀magnetic layer.(2)With the same thickness of the Fe₁₀Co₉₀magnetic layer,the peak position field of the FINEMET(twin surface)/Fe₁₀Co₉₀composite ribbon is smaller than the peak position field of the FINEMET(smooth surface)/Fe₁₀Co₉₀ribbon and FINEMET(rough surface)/Fe₁₀Co₉₀composite ribbon,this is because that both rough surface Fe₁₀Co₉₀layer and smooth surface Fe₁₀Co₉₀magnetic layer simultaneously have a magnetic dipole interaction with the FINEMET ribbon.3.Magnetic dipole interaction in FINEMET/G/Fe₁₀Co₉₀composite materials(1)Under the condition that the number of graphene layers remains unchanged,when the thickness of the Fe₁₀Co₉₀magnetic layer changes from 10 nm to 60 nm,the peak position field of the FINEMET/G/Fe₁₀Co_90[t]composite ribbons first decreases and then increases.This may be related to the effect of the magnetic dipole interaction and stress between the FINEMET ribbon and Fe₁₀Co₉₀magnetic layer.(2)In the case of controlling the thickness of the Fe₁₀Co₉₀magnetic layer unchanged,as the number of graphene(G)layers increased,the magnetic susceptibility of the FINEMET/G_N/Fe₁₀Co₉₀composite ribbon decreased,the coercive force increased,and the magnetic anisotropy field increased.This was because the magnetic dipole interaction becomes smaller,so that the regulation effect on the composite ribbon became weaker and weaker.(3)The research results showed that the magnetic dipole interaction did not obviously modulate the magnetization reversal of the FINEMET/G/Fe₁₀Co₉₀composite ribbon.The reason is that the magnetization reversal mechanism was mainly affected by the demagnetizing field rather than magnetic dipole interaction.