Mixed-Surfactants as a Novel Approach to Atomic Engineering of Spin Valves
D X. Yang, H D. Chopra, P J. Chen, William F. Egelhoff Jr.
Previously, surfactants in ultra-high vacuum have been used to obtain smooth interfaces in giant magnetoresistance effect (GMR) spin valves for an enhanced GMR. In the present study, a novel extension to the surfactant approach has been developed, called mixed surfactants . Instead of a single atomic species as a surfactant, mixed surfactant consists of two or more surfactant species. To test the idea of mixed surfactants, dc magnetron sputtered NiO/Co/Cu/Co bottom spin valves were studied with and without an equi-atomic alloy of Ag0.5Pb0.5 as a mixed surfactant. Results show that at Cu spacer thickness of 1.8 nm, the samples show a small or negligible GMR effect (0.5%) in surfactant-free samples. In contrast, spin valves with a 0.5 to 1.2 monolayer (ML) of surfactant AgPb deposited on the pinned Co layer exhibit more than 20-fold increase in GMR (10-11.5%). The given surfactant work best when deposited on the pinned Co layer. The use of mixed surfactants illustrates their efficacy in favorably altering the magnetic characteristics of GMR spin valves, and their potential use in other magnetoelectronics devices and multilayer systems.