Short-period oscillations of the resistivity and magnetoresistance in Co/Cu(111) superlattices on mica

In a study of [Co(8 A)/Cu(d(Cu))(111)](20) superlattices grown by magnetron sputtering it is found that the resistivity rho(s) and relative magnetoresistance Delta R/R-s in magnetic fields H=15 kOe oriented parallel or perpendicular to the layers exhibit oscillations as the thickness of the copper spacer layers is varied in the range d(Cu)=6-40 A. Extrema of rho(s) and Delta R/R-s are observed at d(Cu)=nd((111)), where n is an integer or half-integer and d((111))=2.087 A is the distance between (111)Cu planes, with a distance between adjacent maxima or minima equal to 1, 1.5, 2, 2.5 and 3d((111)). When the magnetic field deviates from the plane of the layers the magnetic-field dependence of the resistivity exhibits an additional maximum due to a feature of the magnetization of the layers in the superlattice in an inclined field. The oscillations of rho(s) and Delta R/R-s are accompanied by oscillations of the magnetic anisotropy constants in synchrony with them. Analysis of the experimental data and theoretical calculations of the orientation of the magnetic moments of the layers when a magnetic field perpendicular to the layers is turned on allows one to explain the observed effects wherein the roughness of the interfaces between layers varies nonmonotonically with increasing d(Cu), leading to oscillations of the bilinear and biquadratic exchange interactions of the Co layers. (C) 2005 American Institute of Physics.