MAGNETORESISTANCE OF SYMMETRICAL SPIN-VALVE STRUCTURES

A spin valve configuration is presented in which an unpinned ferromagnetic film is separated from exchange-pinned ferromagnetic films on either side by two nonmagnetic spacers, thereby creating a symmetric spin valve structure. The symmetric spin valve is shown to increase the magnetoresistance by 50% over the values of individual spin valves. The increase is attributed to a reduction of spin-independent outer boundary scattering and doubling the number of spin-dependent scattering interfaces. The magnetoresistance and coupling fields of the spin valves that comprise the symmetric structure have been measured as a function of Cu spacer thickness. oscillatory antiferromagnetic to ferromagnetic coupling was observed in standard spin valves, which had Delta R/R as high as 13%.