Area scaling of planar ferromagnetic tunnel junctions: From shadow evaporation to lithographic microfabrication

In order to meet the requirements for applications in magnetoelectronics (e.g., read heads and magnetic random access memory), a processing scheme for micron-scale ferromagnetic tunnel junctions has been developed. A comparative study of junctions defined by shadow evaporation and by lithographic processing was made, where a similar resistance-area product of nearly 1 G Omega mu m(2) and a high tunnel magnetoresistance of up to 15% at room temperature were observed for Co/Al2O3/Ni80Fe20 junctions patterned by both methods. A bipolar sensor characteristic at zero field was realized by inducing anisotropies in the two ferromagnetic layers that are orthogonal to each other. (C) 1998 American Institute of Physics. [S0021-8979(98)50111-9].