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)/Co68Fe5S i12B15 (5 nm)/Ti (6 nm) structures have been deposited by magnetron sputter ing technique onto oxidised Si wafers. Magnetic, magneto-optic characterist ics and magnetoresistance in perpendicular direction of the deposited layer s have been investigated by inductive integrating loop tracer, transverse K err 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 o f 3-4 Oe. Besides, magnetic and magneto-optic measurements showed that the structures can reveal either single-film or double-film properties dependin g on insulator thickness, with the magnetisation reversal characteristics w hich were found to be magnetic field strength dependent. The synthesised st ructures 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.