The Study Of Effects Of Temperature And Content On Micro-magnetic Structure Of Fe-V Alloys

Magnetism,one of the fundamental physical properties,has a wide range of application value.Currently,magnetic products of various kinds have be developed and used,which enjoys strong growth especially in military equipment,high precision sensors,magnetic recording,etc.In recent years,a new concept of "Magnetic-order Strengthening",developed by T Wantanabe,a Japanese professor,has established a connection between the magnetic and mechanical property of a material.After Professor T Wantanabe summed up the results of his experiment of Fe-Co,Fe-Cr and Fe-Mo alloy,he found that temperature and content are two factors in the macro level that can impact the intensity of Fe-based magnetic alloy.Whether it's content or temperature,their impacts are both conducted through influencing the micro-structure of Fe-based magnetic alloy,including electronic structure and the structure of magnetic domain,etc.Previous studies have found that Fe-V alloy,as a magnetic alloy,also demonstrates the phenomenon of "Magnetic-order Strengthening",described by Professor T Wantanabe,To illustrate the impact on the magnetic property of Fe-V alloy caused by content and temperature,this paper analyses the variation of magnetic property of Fe-V alloy through performing experiments and first principle calculation.In the experiment part,we use XRD to measure the variation of lattice constant,VSM to measure the saturation magnetization and MFM to observe the magnetic domain structure of the alloy samples.Results have shown that as temperature rises,saturation magnetization of the alloy declines and that when the temperature reaches around 625 ?,there is a turn in the declining trend.When it's above 625 ? saturation magnetization declines faster as the temperature rises.Similar results have shown in the observation of magnetic domain structure,the variation of which in Fe-V alloy can be divided into two phases.When it's below 625 ?,as the temperature rises,the variation of magnetic domain structure mainly embodies the narrowing of magnetic domains.When it's above 625 ?,as the temperature rises,the length of striped magnetic domains decreases and in the neighboring magnetic domains,spontaneous magnetization decreases,its orientation differences also decline,and the domain structure becomes vague.The composition of the alloy can also affect its magnetic property.When the content of V increases,the saturation magnetization declines and the domain can be narrowed.In calculation part,we established crystal models and cluster models to perform simulation experiments on Fe-V alloy respectively.The results have shown that Fe atoms and V atoms couples antiferromagnetically,so the atomic magnetic moment of some Fe atoms can be offset by the one of V atoms.This can explain,from a macro perspective,that the increase of V content can lead to the decline of the saturation magnetization of the Fe-V alloy.Besides,in the cluster model,we've found that when V atom is in the body-center of and on the vertex of the cluster,the magnetic interaction between V atom and Fe atom changes.When V atom is in the body-center of the crystal,Fe atom and V atom couples antiferromagnetically;when V atom is on the vertex of the cluster,the atomic magnetic moment of the two atoms is in the same direction.