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 ele ctron-beam evaporation at ultra-high vacuum were studied. It was found that buffer layer plays a very important role in the giant magnetores istance 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 roo m temperature. Decreasing temperature to 80 K, the same sample present ed a MR ratio of 15.5% with a maximum MR slope 0.55%/Oe. After anneali ng at 400 degrees C for 10 min, MR ratio was reduced to 1.8% at room t emperature. Atomic force microscope images showed that the grain size at the surface was greatly enlarged. (C) 1998 Elsevier Science Ltd.