Alteration of tunneling mechanism due to ferromagnetic insulator on Andreev spectroscopy for ferromagnet/superconductor junctions

Abstract

We have theoretically elucidated the mechanism of the peak splitting of the tunneling conductance arisen from the effect of ferromagnetic insulator in ballistic ferromagnetic metal/superconductor junctions. On this peak splitting of the tunneling conductance, we have found that the exchange potential in the insulator gives crucial changes to the tunneling conductance through the coherence factor in superconductor. The peak splitting exists even though ferromagnetic metal is replaced by normal-metal. Moreover, in such junctions, the magnetization in ferromagnetic metal gives asymmetric tunneling conductance spectra between electron and hole injections. We have also clarified the difference of resultant influences of ferromagnetic insulator on tunneling conductance between spin-band asymmetry ferromagnet and standard Stoner ferromagnet junctions.