Studies On The Spin Dependent Transport Properties In Fe-ITO Thin Films

Spintronics is a new field of electronics,which is not based on conduction by electrons or holes as in microelectronics,but on the different transport properties of majority and minority spin electrons,and it is the spin degree of freedom not the electric charge carries the information.As a basic subject of spintronics,spin dependent transport phenomena has been well studied in both full-metal and metal-insulator systems as multilayers and granular films and new generation of magnetic storage devices has already been developed.However,there is few reports on the spin dependent transport priorities in metal-semiconductor systems.In this study of the spin dependent transport properties in Fe-ITO thin films,the wide band semiconductor indium tin oxide(ITO),which has been widely used in photoelectronics devices because of its transparent and high conduction and typical ferromagnetic metal Fe has been employed to form both multilayers and granular films.The spin dependent transport phenomena in Fe-ITO system have been studied and the main works are listed as following:(1)A series of Fe/ITO multilayers with different Fe and ITO layers thickness were prepared by DC sputtering method.The magnetic properties,electrical properties and spin dependent transport properties were investigated by vibrating sample magnetometer and magneto-electronic measurement system.(2)The magnetic character of the multilayers can be modified by the ITO layer while the Fe thickness is fixed(3)The temperature dependence of resistively is analyzed and it is the Mott variable range hopping conductance dominates the low temperature conduction(4) Comparing with the ferromagnetic metal/semiconductor multilayers using traditional microelectronic semiconductor Si and Ge,a large Magnetoresistance ration is observed in both room temperature and low temperature.The enhancement of spin dependent magnetoresistance effect is due to the decrease of spin-mixing effect as decreasing the temperature.(5)A break behavior of temperature dependence of resistively and magnetoresistance ratio is discussed.(6) A series of Fe-ITO granular films with different Fe content were prepared by RF co-sputtering method.Atomic force microscope is employed to investigate the surface morphology. The magnetic properties,electrical properties and spin dependent magnetoresistance were investigated by vibrating sample magnetometer and magneto-electronic measurement system.(7)The magnetic character of the granular films changes from superparamagnetic to ferromagnetic as the Fe content increase.(8)The spin dependant magnetoresistance effect is observed in samples with appropriate Fe content.For samples with few Fe content the magnetoresistance curves can be well fitted by the formula of magnetoresistance without inter-granule interaction,while for samples rich of Fe,the magnetoresistance curves is composed of the low-field magnetoresistance contributed to the ferromagnetic large granules and high-field magnetoresistance contributed to the superparamagnetic small granule.And based on above the origin of abnormal dependence of magnetoresistance on Fe content is discussed.(9)As increasing the content of Fe the conduction character of samples change from semiconductors to metals.A abnormal temperature dependence of resistively is observed in Fe -rich samples.