Sandwiched thin-film structures for the magnetoresistive spin-tunnelling sensors

Sandwiched thin-film Ti (80 nm)/Fe19Ni81 (5 nm)/Al2O3 (0.6-1.5 nm)/Co68Fe5Si12B15 (5 nm)/Ti (6 nm) structures have been deposited by magnetron sputtering technique onto oxidised Si wafers. Magnetic, magneto-optic characteristics and magnetoresistance in perpendicular direction of the deposited layers have been investigated by inductive integrating loop tracer, transverse Kerr effect technique and four-point probe method, respectively. It has been found that magnetic layers are coupled with exchange interaction depending on insulator layer thickness that corresponds to magnetic field strength of 3-4 Oe. Besides, magnetic and magneto-optic measurements showed that the structures can reveal either single-film or double-film properties depending on insulator thickness, with the magnetisation reversal characteristics which were found to be magnetic field strength dependent. The synthesised structures demonstrated magnetoresistive spin-tunnelling (MRST) effect up to 5% under the application of planar magnetic fields in the range of 40 Oe. (C) 2000 Elsevier Science S.A. All rights reserved.