Contribution of current perpendicular to the plane to the giant magnetoresistance of laterally modulated spin values

Giant magnetoresistance (GMR) effects up to 10% have been observed in Co/Cu/FeNi spin valve structures grown onto step bunched vicinal Si(lll)substrates misoriented towards [11-2]. The step bunching is activated using a simple thermal treatment which Il-ads to surfaces where terraces alternate with facets at the nanometer scale. GMR of the spin valve structures is investigated with the current applied parallel or perpendicular to the steps. An in-plane uniaxial magnetic anisotropy is induced in each magnetic layer with the easy axis parallel to the steps. This results in square GMR behavior when the field is applied along the easy axis. Specific features observed when the field is applied along the hard axis are also shown to be the consequence of this anisotropy. When the initial misorientation angle of the substrate becomes higher than 4 degrees, we observe an enhancement of the room-temperature GMR when the current is applied perpendicular to the steps. The origin of this enhancement is discussed based on the temperature dependence of this effect. (C) 1997 American Institute of Physics.