ELECTRIC-FIELD CONTROL OF GIANT MAGNETORESISTANCE IN SPIN-VALVES

It has been known that magnetic properties of a ferromagnet grown on piezoelectric substrates can be altered by the electric field-induced strain. We consider spin-valve CoFe/Cu/CoFe/IrMn grown on (011)-cut piezoelectric Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) substrate and investigate the effect of the electric field on the giant magnetoresistance (GMR) of the spin valve. We found that the electric field induced strain on PMN–PT substrate enhances the coercivity of the magnetic layers. The transport measurement shows that the GMR ratio of the spin valve could be altered as much as 50% for an electric field of -8 kV/cm. The change of GMR is attributed to the reduced maximum degree of the antiparallel alignment between the magnetization directions of the free and pinned layers. The present studies establish a prototype electrically tunable magnetic memory device such that the electric field can reversibly tune spin valve magnetoresistance without deteriorating electric and magnetic properties.