OSCILLATORY MAGNETIC COUPLING AND MAGNETORESISTANCE IN CO/RE SUPERLATTICES

We have studied the magnetoresistance (MR) properties of sputtered Si/Re 50 angstrom [Co 20 angstrom/Re x angstrom]40 superlattices with x(Re) = 3-32 angstrom. Transverse and longitudinal MR exhibit oscillation of the interlayer coupling as a function of Re layer thickness with a period of congruent-to 12 angstrom and a maximum transverse MR of congruent-to 1.2% for x(Re) = 5 angstrom at 4.2 K. The saturation magnetic field B(s) and MR magnitude DELTA-R/R for samples with x(Re) = 5 and 7 angstrom 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 X(Re) less-than-or-equal-to 7 angstrom (strong antiferromagnetic coupling) to positive for those with x(Re) greater-than-or-equal 10 angstrom.