Spin Transport in Hybrid Nanostructures

Abstract

In this chapter, we discuss the basic aspects for the spin transport in hybrid nanostructures containing normal conducting metals and transition-metal ferromagnets by focusing on the spin current and spin accumulation in a nonlocal spin device of F1/N/F2 structure, where F1 is a spin injector and F2 a spin detector connected to N. We derive basic spin-dependent transport equations for the electrochemical potentials (ECPs) of up-spin and down-spin electrons, and apply them to the F1/N/F2 structure with arbitrary interface resistance ranging from a metallic contact to a tunneling regime. že injection of spin-polarized electrons and the detection of spin current and accumulation depend strongly on the nature of the junction interface (metallic contact or tunnel barrier) in the structure. By analyzing the spin-dependent transport in the structure, weshow that the relative magnitude of the electrode resistance to the interface resistance plays a crucial role for the spin transport in the F1/N/F2 structure. When a tunnel barrier is inserted into the junction interfaces, spin injection and detection are most e¥ective. When the N/F2 interface is a metallic contact, the injected spin current from F1 is strongly absorbed by F2 (spin sink) owing to small spin resistance of ferromagnets. že spin absorption e¥ect plays a vital role in nonlocal spin manipulation. We present the spin Hall e¥ect (SHE) in nonmagnetic metals caused by spin-orbit scattering of conducting electrons, which enables the interconversion between the spin (charge) current and charge (spin) current using a nonlocal spin device. Spin injection into a ferromagnetic insulator (FI) is brie¦y mentioned.