Effect of annealing on magnetic and structural properties of Co/Re superlattices

We have studied the effect of annealing on the magnetic and structural properties of sputtered Si/Re50 Å [Co20 Å/RexÅ]40 superlattices with xRe=3,5,7,10 Å. Annealing the samples for 1 h at 300 °C causes a slight increase in interfacial mixing and a contraction of lattice spacing d(002) owing to interdiffusion and structural relaxation, as indicated by the x-ray diffraction data. In addition, the subsequent room-temperature magnetoresistance (MR) increases for samples with antiferromagnetic (AF) coupling, by up to 20% for xRe=5 Å, providing strong experimental evidence for the spin-dependent scattering mechanism which predicts an increasing MR with increasing diffuse interface scattering. A further 1 h anneal at 525 °C provokes dramatic interdiffusion between the Co and Re layers, which is accompanied by a considerable decrease of the MR, indicating a disappearance of the interlayer AF coupling.