The Study On Long-range Coupling Interaction Of Cobalt And Non-magnetic Transition Metal Tri-layer Nanocomposite Films

Nano-magnetic multilayer composite films have always played an important role in the research of spintronics,the development of magnetic sensors and magnetic storage devices.With the rapid development of the information age,various spintronic devices have enriched and improved people’s lives.In recent years,more and more researchers have carried out in-depth research on the topic that charge flow induces spin current.The spin current is generated through a non-magnetic heavy transition metal layer,and then the cobalt-based ferromagnetic layer is adjusted to realize the reversal of the magnetization direction.However,in many research processes of these nanomagnetic multilayer films,the capping layer is only used to provide chemical protection for neighboring magnetic layer,and the buffer layer is only used as a liner to form a good structure for the entire film.Nevertheless,few people have studied the long-range coupling interaction between the non-magnetic transition metal capping layer and neighboring magnetic layer.In this paper,through the study of the tri-layer composite film of cobalt and non-magnetic transition metals,the coupling interaction of the paramagnetic electrons of some non-magnetic transition metals and the local electrons of cobalt will be explored to make people re-understand that the non-magnetic transition metal buffer layer and capping layer effect on the magnetic moment of cobalt-based nanomagnetic composite films.The first chapter,from the theoretical model and achievements of the research on the magnetic coupling of transition metals and the applications of spintronic devices,mainly introduces RKKY exchange interaction,giant magnetoresistance effect,spin valve,tunnel magnetoresistance effect,magnetic random access memory,and the research ideas and experimental designs in this paper.The second chapter mainly introduces the experimental ways,process parameters and test methods of the tri-layer nanocomposite film of cobalt and nonmagnetic transition metal.In the experiment,we used magnetron sputtering to deposit nanocomposite films.In this chapter,we introduced in detail the working principles and experimental conditions of related equipments.In addition,the improvements of experimental equipments and procedures were also explained.The testing processes are mainly divided into three parts,testing the thickness of the film with Profilometer,the M-T curve with VSM,and the thin film crystal structure with X-ray polycrystalline diffractometer.Chapter 3 is the experimental results and data analysis.We tested the M-T curves of Ta/Co/Ta structure films under different Co thickness conditions and found a nonmonotonic change trend of magnetic moment with temperature.By changing the elements of the transition metal layers,we conducted comprehensive analysis and reasonable speculation on the cause of this change trend.Around 700 K,the magnetic moment transition behavior of cobalt is significantly affected by the elements of the capping layer.Moreover,this effect can be shown by the coupling effect of the conduction electrons of the transition metal layer and the localized electrons of the Co ferromagnetic layer,indicating long-range.In addition,with the X-ray polycrystalline diffraction spectrum,we tested the samples and found that this special phenomenon exists in the Ta/Co/Ta tri-layer composite film of the amorphous structure.Chapter 4 is the summary and prospect of the experiments in this paper.In this part,we reviewed the research ideas of this paper and summarized the experimental results.At the same time,we prospected the significance of this research and the current research hotspots of nanomagnetic multilayer films.