Electrochemical Preparation and Giant Magnetoresistance Effect of Spin-valve Multilayers

Abstract

[Ni_(80)Fe_(20) /Cu/Co/Cu]_n spin-valve multilayers were fabricated onto n-Si(111) substrates covered with NiFe buffer layers by means of double bath potentiostatic electrodeposition. The electrochemical conditions were determined. A well-defined superlattice structure was characterized by high-angle X-ray diffraction, and the influence of NiFe buffer layer upon the orientation of crystalline growth was studied. Magneto-transport properties of the spin valves were investigated by four-probe technique. Hysteresis loops were tested by vibrating sample magnetometer (VSM) at room temperature. With the increase of the Cu layer thickness (t_(Cu)), giant magnetoresistance(GMR) ratio showed a periodical oscillation at first and achieved the maximum at tCu=3.6 nm, then declined gradually. With the increase of the Co and NiFe layer thickness, GMR ratio rose at first, and dropped after the peak point. The maximum room temperature GMR ratio of 5.4% was obtained with a sensitivity up to 0.2%·Oe~(-1) and a saturation field of 350 Oe for NiFe(25 nm)/[Cu(3.6 nm)/Co(1.2 nm)/Cu(3.6 nm)/NiFe(2.8 nm)]_30 structures.