Magnetoresistance Properties And Mechanism Of Co-TiO₂ Nanoparticle Composite Films

As a kind of spintronic materials with good application prospects,the research of nanoparticle composite films has attracted more and more attention.For composite films of nanoparticles,metal content,size distribution,magnetic metal valence and other factors have important effects on electron transport in the materials.The microstructure and relative content of spintronic materials can be controlled by adjusting the preparation conditions and post-treatment technology.In this paper,Co-TiO₂ nanoparticle composite film was prepared by means of magnetron co-sputtering.The microstructure,electrical and magnetic properties and related electron transport mechanism of the material were studied by parameters such as sputtering power,substrate temperature,sputtering atmosphere and gas pressure.The influence of bias voltage and substrate temperature on the electron transport process of the material was analyzed,and the influence factors of electron tunneling mechanism at low temperature were quantitatively calculated.Its main conclusions are as follows:(1)Co nanoparticles with hexagonal crystal structure in Co-TiO₂ nanocomposite film are dispersed in amorphous titanium oxide matrix.The crystallinity of metal Co in the material can be significantly improved by increasing metal content and substrate temperature.(2)The microstructure of the film can be significantly changed by adjusting the sputtering power and substrate temperature,and the properties of the material's magnetism,electricity and magneto-resistance can be affected by the content of magnetic phase in the film,the size of metal particles and the distribution of particles.(3)As the substrate temperature increases,the metal particles in the film gradually grow up.On the premise of not changing the relative content of magnetic metals,the corresponding saturation magnetization increases from 0.13 to 0.43 T,and the performance is improved by 230%.(4)Bias voltage and test temperature have an important influence on the electron transport process of composite films of nanoparticles.With the increase of bias voltage and test temperature,electrons have a trend of gradually changing from tunneling mechanism to high-order inelastic jumping mechanism.(5)The spin-related tunneling phenomenon of the thin film at low temperature makes the magnetoresistance highly dependent on the test temperature,and finally up to 30%of the tunnel magnetoresistance can be measured at 2 K.At low temperature,indirect electron interaction and coulomb interaction play an important role in electron tunneling.