Study on magnetoresistance coercivity and aging for [FeNi/Cu/Co/Cu]_N spin valve multilayered films

Spin valve [FeNi/Cu/Co/Cu]_N multilayers were prepared using the electron beam method. The influence of the thickness of magnetic and nonmagnetic layers, preparation process, and coercive force H_c on the magnetoresistance (MR) were studied. Using fairly optimum preparing technology, we prepared many samples with low center field H₀ in the range of 10-20 Oe, the MR merit is larger than 0.2%/Oe, where H₀ is the center magnetic field of the linear region in the MR-H curve. The variation of MR in this linear region is reversible during repeated magnetizing. The change of MR is smaller than 1% for several samples after aging for one year in a dry air chamber at room temperature. Moreover, the MR value decreases greatly when Cr or Cu is added into the Co layer, or Co layers are replaced by SmCo₅ magnetic layers.