Oscillatory magnetic coupling and magnetoresistance in Co/Re superlattices

We have studied the magnetoresistance (MR) properties of sputtered Si/Re 50Å[Co 20 Å/Re x Å]40 superlattices with xRe=3–32 Å. Transverse and longitudinal MR exhibit oscillation of the interlayer coupling as a function of Re layer thickness with a period of ≂12 Å and a maximum transverse MR of ≂1.2% for xRe=5 Å at 4.2 K. The saturation magnetic field Bs and MR magnitude ΔR/R for samples with xRe=5 and 7 Å are nearly constant up to 40 K, above which they decrease approximately linearly with increasing temperature. In addition, the perpendicular MR in magnetic fields up to 1 T changes sign from negative for samples with xRe≤7 Å (strong antiferromagnetic coupling) to positive for those with xRe≥10 Å.