| In this paper,the development of magnetoresitance,principle and appliance of magnetoresitance effect were summarized and magnetoresitance effect of manganese oxides were studied.The crystal and electronic structure of manganese oxides compound,as well as the interaction between double-exchange and super-exchange, the model of polaron,theory of crystal field and Jahn-Teller effect were elucidated. The influence factor of magnetic materials and the interaction between different ferromagnets were investigatedThe sample series of La2/3Sr1/3Mn1-xO3(LSMâ–¡O),La2/3Sr1/3Mn1-yFeyO3 (LSMFO),La2/3Sr1/3Mn1-x-yFeyO3(LSMâ–¡FO) and LSMO/xMZF(Mn0.5Zn0.5Fe2O4) were prepared by solid phase reaction method and the structure and phase of samples were carried out by X-ray diffraction instrument Bruker D8 made in Germany.Lattice parameters were obtained from X-ray by the software Jade5.0.The microstructure of samples were observed by scanning electron microscopy H-3000 made in Japan.The temperature dependence of magnetoresistance(MR) were measured by VSM.The maximal magnetoresistance was obtained in the point of Tc from the magnetoresistance curve.The results of X-ray diffraction patterns shows that lattice constants of three series of samples used by solid phsae reaction method change little and perovskite orthorhombic structure with single phase are kept as the doping concentration icreases.The crystal structure of Fe-doped LSMFO have not grown well and the crystal had evident aperture,which is probably attributed to low sintered temperature. The resistivity of samples LSMâ–¡FO increase monotonously and its Curie temperature discrease as temperature increases,which is due to the lowering of the double-exchange interaction between Mn3+ and Mn4+ and thus causes the increase in mangnetoresistance.The resistivity of LSMO/xMZF increases as doped increase,which is due to the Formative tunneling through LSMO/MZF/LSMO tunneling structure.With the increase of doping concentration,low-temperature magnetoresistance increases and high-temperature magnetoresistance decreases.As the doping concentrations increase,LSMO/MZF/LSMO tunnel section percentage gradually increase.At the strong magnetic field were applied,the carriers at low temperature can tunneling through the grain boundary barrier,leading to the increase of magnetoresistance.However,at high temperature,the thermal moving of carriers leads to the spin disorder of LSMO and greatly reduces the spin-dependent tunneling effect,leading to a sharp lowering in magnetoresistance.
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