Theory of the spin-filtering effect in ferromagnet/ferromagnetic insulator/superconductor junctions

Abstract

Although it is well known that the ferromagnetic insulator at the interface of the superconducting junctions works as a spin-filter, its detailed mechanism has not yet been clarified. Here we present a simple factor inducing the spin-filtering effect in ferromagnet/ferromagnetic insulator/superconductor junctions by applying the extended Blonder-Thinkham-Klapwijk theory. From the factor, one can see easily how the spin-filtering effect is induced by the ferromagnetic insulator. Furthermore, it is also shown that the spin-filtering effect can be caused only by ferromagnet without ferromagnetic insulator. As an interesting application, we study the spin-filtering effect for a chiral p-wave superconductor. In ferromagnet/insulator/chiral p-wave superconductor junction, we find that the zero-bias conductance peak is shifted in opposite bias-voltage directions for Stoner model and spin bandwidth asymmetry ferromagents. It is also shown that the additional shift by ferromagnetic insulator may be useful for identifying the dominant mechanism of the Stoner and spin bandwidth asymmetry mixed ferromagnet.

Unconventional Rashba Spin-Orbit Coupling on the Charge Conductance and Spin Polarization of a Ferromagnetic/Insulator/Ferromagnetic Rashba Metal Junction

“…The conductance exhibited a unique behavior in the ARM state when the RSOC and the exchange coupling field are taken into account. The states on the strong spin-orbit interaction are usually influenced by both the intrinsic and extrinsic parameters in the heterostructure and show the important electrical features, such as the current, conductance and the spin polarization [27][28][29][30][31][32][33][34][35][36][37].…”

Robustness in ferromagnetic phase stability, half‐metallic behavior and transport properties of cobalt‐based full‐Heuslers compounds: A first principles approach

“…Current efforts in designing and manufacturing spintronic devices involve two different approaches. The first is perfecting the existing GMR‐based technology by either developing new materials with larger spin polarization of electrons or making improvements or variations in the existing devices that allow for better spin filtering [18]. The second effort, which is more radical, focuses on finding novel ways of both generation and utilization of spin‐polarized currents.…”

“…As a result, they have great technological interest with a wide range of possible applications in fields of spintronics as an electrode material, in thermoelectrics as an active material for conversion of waste heat into useful energy [15][16][17].Current efforts in designing and manufacturing spintronic devices involve two different approaches. The first is perfecting the existing GMR-based technology by either developing new materials with larger spin polarization of electrons or making improvements or variations in the existing devices that allow for better spin filtering [18]. The second effort, which is more radical, focuses on finding novel ways of both generation and utilization of spin-polarized currents.…”