Interdiffusion Behavior And Its Effects On Magnetic Properties Of Co-based Film Diffusion Couples During High Magnetic Field Annealing

Diffusion as an important mass transfer phenomenon in materials science is one of the most basic science issues.Diffusion can affect structural evolution and stable behavior in materials.It is closely related to many physical and chemical processes in material processing,such as phase transformation,sintering,solid solution formation,semiconductor doping and so on.Therefore,it is very important to study the rules of atoms migration and diffusion.The dimension of diffusion is close to the thicknesses for films.The surface(interface)-to-volume ratio significantly increases in films.This means that diffusion has a more remarkable and important influence on thin film materials than bulk materials.High magnetic field(HMF)is a special form of magnetic field with extreme condition,which has the features of non-contact,pollution-free,high-energy and so on.HMF can transfer high energy to atomic scale without contact,further influence and change atom molecular alignment,match and migration.Some studies indicate that HMF has a significant influence on bulk materials.HMF is applied to control diffusion in films during annealing in this work.It is expected that the application of HMF will be an effective method to modulate the diffusion behavior in thin films and control the magnetic properties.On the basis of Co films,the influences of HMF on interdiffusion and magnetic properties in Co/Si(100)films composed of Co single layer and Si single crystal substrate,Cu/Co/Si(100),Co/Cu/Si(100)bilayers and Co/Cu/Co/Si(100)trilayers composed of Co and Cu films at different annealing temperatures were investigated in our study.The microstructures,interdiffusion and magnetic properties were studied to reveal the effects of HMF on interdiffusion and magnetic properties in films from the view of magnetic free energy and other factors.The results are as follows.(1)The results of Co/Si(100)films diffusion couples show that HMF accelerates the interdiffusion between Co and Si,decreases saturation magnetization(Ms)and coercivity(He)at annealing temperature of 300 ?.HMF accelerates the interdiffusion between Co and Si,increased Ms and decreases Hc at 350 ?.HMF suppresses the interdiffusion between Co and Si,increases Ms and decreases Hc at 400 ?.HMF accelerates the interdiffusion between Co and Si,increases Ms and Hc at 450 ?.HMF accelerates the interdiffusion between Co and Si,decreases Ms and increases He at 500 ?.HMF accelerates the interdfusion between Co and Si,increases particle size and surface roughness at 600 ?,700 ? and 800 ?.The Kirkendall effect is firstly found in Co/Si(100)film diffusion couples at 600 ?.HMF decreases Hc and had no effects on remanence ratio(Mr/Ms)at 600 ?.HMF decreases Hc and Mr/Ms at 700 ? and 800 ?.(2)The results of Cu/Co/Si(100)bilayers diffusion couples show that Co and Si diffusing into each other plays an important role at annealing temperatures of 300 ? and 400 ?.HMF decreases Ms and has no effects on Hc at 300 0C.HMF increases Ms and Hc at 400 ?.HMF accelerates the interdiffusion between Co and Cu,Co and Si in Cu/Co/Si(100)bilayers,decreases Ms and increases Hc at 500 ?.The results of Co/Cu/Si(100)bilayers diffusion couples show that HMF accelerates the interdiffusion between Cu and Si.The Cu layer as a diffusion barrier is used to suppress the interdiffusion of Co and Si.HMF increases MS and Hc at 300 ?,400 ? and 500 ?.(3)The results of Co/Cu/Co/Si(100)trilayers diffusion couples show that Co and Si diffusing into each other plays an important role at annealing temperatures of 300 ? and 500 ?.HMF has no effects on MS and Hc.HMF accelerates the interdifusion between Co and Cu,suppresses the interdiffusion between Co and Si in Co/Cu/Co/Si(100)trilayers at 400 ?.HMF decreases MS and Hc.(4)The effects of HMF on interdiffusion and magnetic properties of Co-based film diffusion couples after high magnetic field annealing with different temperatures are primarily studied.HMF increases the difference of free energy between new phase and previous phase,provides a driving force for phase transformation of Co films.Magnetic free energy produced by HMF promotes the interdiffusion among diffusion elements.HMF changes magnetic phase content,interdiffusion among elements,alloying extent and defect contents to vary Ms.HMF changes grain size,particle size,surface roughness and alloying extent to decided Hc.Varied phase composition leads to different HMF effects at different annealing temperatures.