The magnetoresistive properties of spin-filter spin valves (SVs) with a synthetic structure were investigated. Spin-filter SV heads were fabricated and evaluated in order to verity the advantages of the spin-filter structure. Spin-filter SV films exhibit a maximum MR ratio for a back-layer thickness of 10 Å, which is larger than that of conventional SV films for a thin free layer of less than 40 Å thickness. In spin-filter SV heads, the asymmetry is adjustable even if the free layer becomes as thin as 20 Å. Therefore, high read-back amplitude and an asymmetry close to zero are simultaneously realized in spin-filter SV heads.
