Giant magnetoresistance in NiFeCo/Cu/Co/Cu/NiFeCo multilayers prepared by electron-beam evaporation

NiFe/Co/Cu/Co/Cu/NiFeCo multilayers grown on silicon substrates by electron-beam evaporation at ultra-high vacuum were studied. It was found that buffer layer plays a very important role in the giant magnetoresistance effect in the simple symmetric structure. Without buffer layer, the magnetoresistance ratio was only 0.4% in the structure. By using a Cr buffer layer 50 Angstrom thick, a largest MR ratio of 8.2% with a maximum MR slope of 0.5%/Oe was obtained for NiFeCo(35 Angstrom)/Cu(30 Angstrom/Co(35 Angstrom)/Cu(30 Angstrom)/NiFeCo(35 Angstrom) at room temperature. Decreasing temperature to 80 K, the same sample presented a MR ratio of 15.5% with a maximum MR slope 0.55%/Oe. After annealing at 400 degrees C for 10 min, MR ratio was reduced to 1.8% at room temperature. Atomic force microscope images showed that the grain size at the surface was greatly enlarged. (C) 1998 Elsevier Science Ltd.