| Silicon steels have attracted wide attention due to their excellent soft magnetic properties and are widely used in the fields of electronic and military industry.There are many kinds of silicon steels,among which the silicon steel containing 6.5%Si has high permeability and saturation magnetization,and its magnetostriction is almost zero.Because of its low iron loss at high frequency,this kind of silicon steel is an ideal material for manufacturing high-frequency motors,high-frequency transformers and choke coils.The control of the micro-domain structure is of great significance to further improve the soft magnetic properties of silicon steel,but there are far fewer studies in this field.Based on the research background above,the static magnetization experiments of 6.5%Si silicon steel with different thicknesses was carried out.The effects of thickness on static magnetism,energy and domain structure were studied by using the principle of minimum energy.The dynamic magnetization models were established according to the LLG equation,and the dynamic magnetization process was analyzed.Meanwhile,The effects of frequency and temperature on magnetic properties,energy and domain structure were studied.The main research results obtained in this work are as follows:(1)The magnetism and domain structure of the initial magnetization stage and the remanence and coercivity stages were studied in the process of static magnetization.Within a certain thickness range,the loss and coercivity increase first and then decrease with the increase of thickness,and the remanence decreases with the increase of thickness.At the initial stage of magnetization,when the thickness exceeds 5.50nm,the vortices in the center move toward the boundary,but under the action of Zeeman energy,the domain structure finally forms "C" state and "flower" state.At the remanence and coercivity stages,the peak values of demagnetization energy and exchange energy disappear when the thickness exceeds 5.50nm,and the "strip" domain structure also disappears.When the thickness reaches 24.75nm,the demagnetization energy first decreases and then increases.However,the exchange energy first rises and then decreases,resulting in the symmetry of magnetic moments and two vortices in the center.(2)The effects of frequency on the magnetic and domain structure of the initial magnetization stage and the remanence and coercivity stages were studied in dynamic magnetization,and the magnetic dispersion phenomenon caused by the relaxation process was found.At the initial magnetization stage of 10MHz,a "double C" domain structure appears.In the initial magnetization and remanence stages,the magnetic moments show "flower" state.At 10MHz and 100MHz,there are two peaks of demagnetization energy and exchange energy,and the energy fluctuates with magnetization time.At 1GHz,there is only one peak of demagnetization energy and exchange energy,the transition and annihilation of vortices are more complex,and the magnetic moments in coercive phase turn to magnetization earlier,and finally no "strip"domain structure is formed.(3)The effects of temperature on the magnetic properties and magnetic moment distribution were studied in dynamic magnetization.The saturation magnetization and remanence decrease with the increase of temperature.At the initial stage of magnetization,the distribution of magnetic moment becomes more chaotic with the increase of temperature when the magnetization time reaches 0.150ns,and there are many small domains and small eddies.When the time reaches 0.225ns,the exchange energy and the small vortices increase with the increase of temperature.At the stage of remanence and coercivity,when the time reaches 5.000ns(the remanence point),the magnetic moments at the center deviate from the direction of the original magnetic field with the increase of temperature,and the "C" structure at the edge becomes less obvious with the decrease of temperature;small eddies still exist at the edge when the time reaches 5.340ns.(4)The change of domain structure of silicon steel with the aspect ratio of 1:1:1 during dynamic magnetization was studied.In the initial magnetization stage,the lower the frequency is,the easier the magnetic moments turn to the direction of the external magnetic field,and the asymmetric "C" structure is formed at 10MHz and 100MHz.At the remanence point of 10MHz and 100MHz,the "strip" domain structure is formed in the heart,while the "flower" domain structure is formed at 1GHz.In the coercive state,"X" domain structure is formed at the frequency of 1GHz.Although "X" domain structure is formed at 10MHz and 100MHz,the thickness of domain wall decreases and the magnetic moments inside the domain wall turn more to the direction of external magnetic field. |
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