MAGNETOSTRICTIVE EFFECTS IN CU CO/CU/FE SPIN-VALVE STRUCTURES/

We have investigated the magnetoelastic response of a series of Cu/Co/ Cu/Fe multilayer films to applied stress by observing changes in the s pin-valve magnetoresistance. The films were prepared by de magnetron s puttering onto glass or polyimide substrates with individual layer thi cknesses ranging from 35 to 50 Angstrom. The typical magnetoresistance without external stress is about 1.2%. The strain induced by the appl ied stress varies from + 1600 (tension) to - 1300 (compression) parts per million. We observed a decrease (increase) of coercivity with comp ressive (tensile) strain for both Fe and Co. This indicates that in th e film plane, Fe and Co films have the same positive sign of magnetost riction. The observed coercivity change is about +/- 10 Oe for the max imum applied strain in both cases. The resulting maximum change in Del ta R/R with a 1% strain is about - 0.018 (+ 0.012) at the coercive fie ld of Fe (Go).