Electronic Transport Properties In Co-based Magnetic Nano Granular Thin Films

With the electromagnetic components turn toward to miniaturization,thinning,integration and other directions,the performance requirements for detecting,transmitting and processing a wide range of information are greatly enhanced to the materials of electronic devices.Single material cannot meet the increasingly diverse performance requirements.Developing new composite materials is a choice to improve the overall performance of materials.Among composite materials,granular film is a new type of artificial nanocomposite functional material which is worthy of attention.The electrical transport properties in the granular film are closely related to the material type,particle composition,particle size,particle spacing,barrier between particles,and the measuring temperature.Researches about the microstructure and electrical transport properties have been a hot topic in academic field.A series of Co-Si,Co-Al2O3 and Co-Cu granular thin films with a thickness about 100 nm and different Co volume fraction have been prepared by magnetron co-sputtering.The influence of film composition,surface morphology,particle structure and interparticle interface to the electrical transport properties of Co-based granular thin films have been studied systematic.The main results are as follows:(1)Co nanocrystal particles are well-distributed among Si amorphous matrix in Co-Si granular thin films,resulting in much interface among Co particles and Si matrix.Various conducting mechanisms have been found in films with different Co concentrations,a FIT and temperature-dependent scattering have been found with x>0.36,while a FIT model has been found with x?xc.Hall effect has been enhanced obviously with introducing Si.The saturated anomalous Hall resistivity increases from 0.11 ?? cm with x=1 to 2.86 ?? cm with x=0.4,while the Hall sensitivity increases from 0.82??)cm/T with x=1 to 7.16?? cm/T with x=0.36.(2)The conducting mechanism varies in Co-Al2O3 granular thin films with different Co volume fractions and measuring temperatures.When x>0.5,FIT and temperature-dependent scattering dominate the main conducting mechasism.The conducting mechanism varies at different measuring temperatures when x<0.5,a FIT model has been found with a positive TCR,when TCR<0,the relation between resistivity and temperature can be fitted with the hopping conducting model of Abeles and his coworkers.The magnetoresistance increases to about 5%with a Co volume fraction of 0.4 while the saturated anomalous Hall resistivity has been enhanced nearly 22 times with x decreases from 1 to 0.5.(3)Nanocrystal Co particles and crystal Cu particles are well-distributed in Co-Cu granular thin films,causing clear boundaries among particles.The anomalous Hall effect firstly increases then shows a downward trend as continuous increase of Co concentration.The scaling relation between saturated anomalous Hall resistivity(?Axy)and resistivity(?xx)can be described by equation of ?Axy??nxx,the values of n are 2.01,4.34,4.32 and 4.56 for x=1.085,0.73 and 0.65,respectively.