In-plane anisotropy in Fe/Co/Cu/Co spin valves

Uniaxial magnetic anisotropy was found in the Fe/Co/Cu/Co magnetoresistive structures deposited on Si(100) substrates. Samples magnetized along an easy anisotropy axis showed extremely sharp magnetization and magnetoresistance switching at low fields and maximum giant magnetoresistance of 9.5% at 5K (5.5% at room temperature) for the samples with 5 nm of Fe, 5 nm of Co, 2.5 nm of Cu and 2 nm of Co. These results were advantageous compared to Co/Cu/Co trilayers grown on Cr/Cu buffer which did not exhibit uniaxial anisotropy. Deposition on spinning wafers allowed excluding substrate related anisotropy. Spin-valves deposited on stationary wafers tilted with respect to the beam of deposited materials did not give any evidence for the relation between the angle of incidence and tilted columnar growth in the spin valves. An existing magnetic field in the magnetron sputtering system with the strength of 32 Oe at the sample location was found the most probable source of the induced uniaxial anisotropy.