Hard magnetic CoCr layer in ferromagnetic tunnel junctions

In magnetic tunnel junctions a highly spin-polarizing layer is usually exchange biased by an antiferromagnetic layer, an artificial antiferromagnetic layer system or a combination of both, while the magnetically soft layer is free to rotate. The use of a single layer of a hard magnetic material is rarely investigated up to now. In this paper, we present the electric and magnetic properties of tunnel junctions with a hard magnetic Co83Cr17 layer. The soft magnetic electrode consists of either a single Co layer or a Co/Ni80Fe20 bilayer. The magnetic anisotropy and coercive field H-subset of. of the CoCr layer depend on its thickness and the kind of the bottom layer (Cu or Ta) and can vary from H-subset of = 50-700 Oe. It is found that a thin Co cap layer also influences the hysteretic behavior. Furthermore, only small changes after annealing up to 450 C promise a high thermal stability for the application in magnetic tunnel junctions. Measurements of the tunnel magnetoresistance on large area junctions, however, show a strong magnetic coupling of the hard and soft electrodes. (C) 2002 Elsevier Science B.V. All rights reserved.