Oscillatory exchange coupling and strong direct tunnelling with AgCl based heterojunctions

The structural stability and ground state electronic properties of Fe/AgCl/Fe (0 0 1) junctions with c(2 × 2) Fe/AgCl (0 0 1) heterointerfaces are studied by means of ab␣initio surface Green's function technique for surface and interfaces. The spin-resolved ballistic conductances across Fe/AgCl/Fe (0 0 1) heterojunctions are determined by using Kubo-Landauer approach. Total energy calculations show that sharp Fe/AgCl (0 0 1) interfaces are possible. The interfacial charge transfer is interface sensitive and generates electrostatic interactions that contribute to the stabilization of Fe/AgCl (0 0 1) interfaces. The magnetism of interfacial Fe layers is robust but is responsive to the interfacial structure. The exchange coupling between Fe electrodes across AgCl barriers shows unexpected oscillations with respect to the spacer thickness that may be related in part with the amount of metal induced gap states in AgCl spacers. A powerful Δ1 spin filter effect is evidenced across AgCl barriers. Depending on the interface structure, large magnetoresistance ratios, above 3100%, are predicted. Interfacial interdiffusion may affect the magnetoresistive properties. The lower lattice mismatch at c(2 × 2) Fe/AgCl (0 0 1) interfaces combined with the strong Δ1 direct tunnelling across AgCl barriers make Fe/AgCl (0 0 1) interfaces attractive in the context of magnetoelectronics.