Study On Preparation And Magnetic Properties Of Lithium Ferrite Thin Films

With the development of science and information storage,the requirements are also increasing for low cost,high efficiency and low power consumption of functional devices.Traditionally,metal magnetic materials were widely used for information processing and transmission,while it will inevitably be produced Joule heat in the process of information processing,which will increase the power consumption of devices and reduce the life of devices.Therefore,it is very important to find a material that can reduce the power consumption and improve the efficiency of devices.Microwave ferrites have attracted extensive research interests of researchers due to their excellent properties such as high resistivity and low eddy current losses,and are widely used in microwave devices and magnetron spintronics.In this paper,the magnetic properties,electric field-modulated magnetic properties and spin transport properties of spinel lithium ferrite（LiFe₅O₈）thin films were systematically studied.The main conclusions are as follows:LiFe₅O₈ thin films with high quality were successfully grown on a（001）single-crystalline MgO substrates by pulsed laser deposition（PLD）technique.The crystal structure,surface morphology and static magnetism of LiFe₅O₈ thin films grown at different temperatures were characterized by high resolution X-ray diffraction（HRXRD）,atomic force microscopy（AFM）,vibrating sample magnetometer（VSM）and ferromagnetic resonance measurement（FMR）,respectively.The results indicate that controlling the growth temperature of the films is an effective method to tailor the lattice parameter and further modify the magnetic properties of the epitaxial LiFe₅O₈thin films.Epitaxial LiFe₅O₈ thin films were grown on a（001）piezoelectric Pb(Mg_1/3Nb_2/3)_0.7Ti_0.3O₃（PMN-PT）substrate by using PLD technology.We have been studied the spin current transport measurements in LiFe₅O₈/Pt heterostructure.The angular dependence of the magnetoresistance curves in LiFe5O8/Pt heterostructure is attributed to the typical spin Hall magnetoresistance（SMR）effect and the magnetic proximity effect is negligibly small.Meanwhile,the SMR in LiFe5O8/Pt heterostructure is systematically investigated over a wide range of temperature.It reveals that the magnitude of the SMR increases from 1.1×10^-4 to 1.8×10^-4 with 9 T external magnetic field as the temperature increases from 10 K to 300 K.Our work clearly proves that the spin backflow from LiFe5O8/Pt interface can also be observed,which provides more choice of magnetic insulator materials in spintronics application.We realize a strong non-volatile electric field control of the magnetism by the FMR measurement in LiFe₅O₈/PMN-PT heterostructure.Interestingly,a hysteresis loop like shape for the relationship between resonance field and the applied electric field was found in the LiFe₅O₈/PMN-PT heterostructure,which the differences of the resonance field between the positive and negative remnant polarization state were up to 250 Oe.Reciprocal space mappings study of piezoelectric control of magnetism origin from the change of the microstructure enhanced further the understanding of non-volatile magnetic responses to ferroelectric domain switching.These findings illustrate that applying electric field to the LiFe₅O₈/PMN-PT heterostructure is an effective way to tailor the magnetic properties of LiFe₅O₈ film and make it a competitive candidate for high frequency and high temperature applications in isolators,circulators,and phase shifters.