Magnetoresistance in tunnel junctions using Co2(Cr,Fe)Al full Heusler alloys

We grew Co-2(Cr1-xFex)Al Heusler alloy films using a magnetron sputtering system on thermally oxidized Si substrates at room temperature without any buffer layers. The x-ray diffraction patterns did not show the L2(1) structure as expected for the bulk but revealed the B2 and A2 structures, depending on the Fe concentration x, in which the structure tends to become the A2 with increasing x. The magnetic moment and the Curie temperature monotonically increased with increasing x. Spin-valve-type tunneling junctions consisting of Co2Cr1-xFexAl (100 nm)/AlOx (1.4 nm)/CoFe (3 nm)/NiFe (5 nm)/IrMn (15 nm)/Ta (10 nm) were fabricated on thermally oxidized Si substrates without any buffer layers using metal masks. The maximum tunneling magnetoresistance at room temperature was obtained as 19% for x=0.4. (C) 2004 American Institute of Physics.