Influence Of Material Structure On Magnetic Properties

In recent years,with the development and utilization of nanomaterials,the relationship between material structure and physical properties has been paid more and more attention.In order to improve the magnetoelectric of multiferroic material,a large number of structural integration appeared,especially the study of multiphase composite multiferroic materials has become a research hotspot in the field.The study found that the magnetoelectric effect was enhanced,but the mechanism was unknown;in addition,in order to study the physical mechanism of room temperature ferromagnetism appears in non-magnetic metal oxide,various attempts have been made,and find that the structure has an important influence on this kind of ferromagnetic material,but the physical mechanism still does not have a unified conclusion.In order to solve the above problems,the multi phase composite multiferroic materials and ordered porous ZrO₂ thin films were prepared.Specific results are as follows:By changing the content of ferrimagnetic phase CoFe₂O₄?CFO?with spinel structure,a series of multiferroic material Bi_0.85La_0.15FeO₃?BLFO?and CFO was prepared by solid state reaction method;the structure and composition of materials were characterized by BLFO and CFO using Scanning electron microscopy?FE-SEM?,X ray diffraction?XRD?and X ray energy dispersive spectroscopy?EDS?,found that no chemical reaction in the preparation process,and crystalline size of BLFO changes almost with the ferromagnetic phase doping;The physical properties were tested by physical property tester?PPMS?and ferroelectric analyzer and the results show that,the saturation magnetization and remanent polarization increase with the increase of ferromagnetic phase?CFO?;we assume that magnetic entirely from the ferrimagnetic phase CFO,magnetization intensity of materials were calculated,and comparison with experimental testing,found that the theoretical value is far less than the experimental values,it is proved that there was a strong magnetoelectric coupling in BLFO-CFO composite material;due to the leakage current of the composites is larger,thus the magnetoelectric coupling coefficient can not be measured,the results also provide a new proof method for the existence of the magnetoelectric effect in the composite sample.Ordered porous ZrO₂ thin films were prepared by reactive DC magnetron sputtering on an ordered porous anodic aluminum oxide template?PAA?.The structure and composition of the materials were characterized by XRD,FE-SEM and EDS,it is found that with the increase of sputtering time,the pore size of ZrO₂ thin film become smaller and smaller,and thickness become more thick;The physical properties of ZrO₂ thin films were tested by PPMS and UV visible spectrophotometer?UV-vis?.It was found that the ZrO₂ films showed obvious ferromagnetism at room temperature,and larger magnetic when the external magnetic field perpendicular to the film surface than magnetic field parallel to the film.The results show that ZrO₂ thin films have magnetic anisotropy,and the direction of easy magnetization was along the direction of the hole,moreover,the maximum saturation magnetization of the film with the maximum pore size are about 119emu/cm3;the annealing and PL test results show that the magnetic properties of ZrO₂ films is mainly dependent on single electron oxygen vacancies and the special porous structure in the film,and we can control the number of oxygen vacancies to achieve magnetic changes,it also shows that ZrO₂ films could be well applied to spin electronic devices.