Tunneling magnetoresistance of glass/Co/Al2O3/Fe50Co50/Ni80Fe20 nanostructures with one magnetostrictive layer

Magnetic tunnel junctions of the glass/Co(10 nm/Al2O3(G)/Co50Fe50(1.8 nm)/Ni80Fe20(10 nm) configuration for t(x) from 1.4 to 2.6 nm were fabricated by RF-sputtering. Samples were studied by means of the atomic force microscopy (AFM), high-resolution transmission electron microscopy (HR-TEM) and tunneling magnetoresistance (TMR) measurements. The tunneling magnetoresistance was investigated as a function of the thickness, as well as the oxygen concentration of the insulating layer. The optimum configuration was obtained for t(x) = 1.8 nm. In this case, a magnetoresistance of 12% was reached in an applied field of about 2 mT. From analyses of the I-V characteristics, the effective barrier width and height of the isolator turned out to be equal to 1.5 nm and 1.3 eV, respectively. These magnetic tunnel junctions can be used to design pressure sensors.