Magnetic tunnel junctions of the glass/Co(10 nm/Al2O 3(tx)/Co50Fe50(1.8 nm)/Ni 80Fe20(10
nm) configuration for tx 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 tx = 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.
