The Study On Electric Field Control Of Magnetism In Oxides

Nano-materials have the basic characteristics of small size effect,quantum size effect,surface effect.When the particles of magnetic material enter the nanometer size,they have special properties in terms of physics and chemistry.In recent years,people have become more and more enthusiastic about the research of nano-magnetic materials.The excellent properties and wide applications of magnetic nano_materials are also known by people.With the advancement of technology,multi-functional and miniaturized,high-performance magnetic materials are increasingly in line with the trend of technology development.People have shown great interest in materials with a variety of physical properties.Electronic devices of Magneto-electric coupling have great potential applications,especially in information storage and electronic spin devices.Most of the people are studying multi-ferrous materials.In multiferrous materials,electric field can control magnetism,or magnetic field can control electrical properties.In order to realize high-density,low-power and fast storage of data storage devices,it is desirable to achieve mutual regulation of electrical and magnetic properties in the same device.How to achieve magnetoelectric coupling,and prepare magnetoelectric coupling materials and the physical mechanism of magnetoelectric coupling is the focus of research on magnetoelectric coupling.The thesis has carried on the research of the following several content mainly:1.We prepared Gd3-xDyxFe5O12?x=0,0₃,0.6,0.9?and Gd3-xTbxFe5O12?x=0.3,0.6,0.9?polycrystalline samples by sol-gel method.The effect of the applied different electric field on the magnetization and remanent magnetic was studied.We have found that the electric field can change the magnetic size and flip the magnetic direction of Gd3Fe5O12.It is found that with the increasing of electric field,the time required for the magnetic flip of Gd3Fe5sO12 becomes smaller.By studying Gd3-xDyxFe5O12?x=0,0.3,0.6,0.9?,it is found that the compensation temperature of the material moves toward the low temperature direction with the increase of the Dy doping proportion.Under the applied different electric field,the remanent magnetic decreases below the compensation temperature.Under the applied different electric field,the remanent magnetization increases above the compensation temperature.For the Gd3-xTbxFe5O12?x=0.3,0.6,0.9?polycrystalline samples,it is found that the compensation temperature of the material moves toward the low temperature direction with the increase of the Tb doping proportion.Under the applied different electric field,the remanent magnetization decreases below the compensation temperature;Under the applied different electric field,the remanent magnetization increases above the compensation temperature.2.We prepared GdCrO3 polycrystalline samples by solid state method.The effect of electric field on the remanent magnetization of GdCrO3 materials was studied.It was found that the electric field can regulate the magnetic properties.3.The amorphous NiO/LiTaO3 film exhibits ferromagnetism at room temperature.The amorphous NiO film deposited at the same temperature,the saturation magnetization of the thicker NiO film is smaller than the saturation magnetization of the thinner NiO film,which is mainly caused by the interface effect.The Ms of the film deposited at lower temperature is higher than the film deposited at higher temperature when the film thickness is similar.This phenomenon is expressed by the following two points:The first is that in the high-temperature oxygenation state,the proportion of elemental Ni in the ferromagnetic phase is reduced,and the film deposited at a higher temperature is less magnetic.The second is that there is surface spin in the particles.The film deposited at a higher temperature has a higher degree of crystallization,and the deposited crystal size is larger.The surface spin accounts for a smaller proportion than the lower temperature deposited crystal grains.The ferromagnetic effects of surface spins on higher deposited grains are less than the ferromagnetic effects of lower temperature surface spins.Studies have shown that the magnetic properties of materials are also affected by oxygen vacancies,which we do not rule out.At room temperature,we found that the electric field can regulate the magnetic properties of the amorphous NiO/LiTaO3 film.Applying a positive electric field?pointing from the substrate to the film?can increase the saturation magnetization of the film.