Multilayer Ferromagnetic/from Electron Transport Properties Of The Superconducting Tunnel Junction

With the rapid development of spintronics as well as its application of new-styledevices, the research of transmission characteristics of spin-polarized quasi-particles andthe coexistence between ferromagnetism and superconductivity have become a hot topic inrecent years. In this thesis, we will focus on the Josephson Effect in the ferromagneticd-wave superconductor junctions, and the quantum point contact tunneling spectroscopy inthe normal metal/ferromagnet/d-wave superconductor (N/FM/SC) junction. The specificarrangement is as following:In chapter one, we will briefly introduce basic concepts of the superconductor, thefundamental theory to study superconductor junctions. Besides, some fascinatingphenomenon about the system of superconductor junctions will be demonstrated.In chapter two, by solving a self-consistent equation of the energy gap and theexchange energy in the ferromagnetic d-wave superconducting, we investigate theJosephson current in the ferromagnetic d-wave superconductor junctions. It is shown that1)in the Josephson critical current, there are two oscillation components with differentperiods, and it is found that the two-periods component can be separated from each otherby changing the exchange energy in ferromagnet and varying the barrier strength at theinterface of the ferromagnet/ferromagnetic d-wave superconductor;2) when thealignment of the magnetization in the ferromagnetic d-wave superconductor is parallel, theexchange energy of the ferromagnetic d-wave superconductor may lead to a rise of thecritical current under specific thickness of the ferromagnet; while the alignment of themagnetization is anti-parallel, the critical current will be inhibited for any thickness of theferromagnet.In the third chapter, by applying extended the Blonder-Tinkham-Klapwijk (BTK)approach and solving the Bogoliubov-de Gennes (BdG) equation, we have studiedtunneling spectroscopy of quantum point contact in the normal metal/ferromagnet/metal/ferromagnet/d-wave superconductor (N/FM/SC) junction. Our numerical calculationsdemonstrated that:1) The length of the quantum wire and the orientation of crystal axisaffect the period of oscillation of the tunneling spectroscopy;2) The strength of scattering barrier determines the height of peaks, and the exchange energy of ferromagnet results in ashift of the peak position.