Influence of ion bombardment on transport properties and exchange bias in magnetic tunnel junctions

Magnetic tunnel junctions (Mn83Ir17/Co70Fe30/AlOx/Ni80Fe20) were bombarded by 10-20 keV He+ ions in an applied magnetic field to manipulate the exchange bias of the magnetically hard electrode. The tunneling magnetoresistance of the bombarded junctions is up to 37.8% for ion doses high enough to ensure a well defined exchange bias. This should allow the preparation of high quality tunnel junctions with magnetic micropatterned hard electrodes. For very high ion doses the tunneling magnetoresistance starts to decrease, whereas the area resistance product increases. Possible explanations based on structural alterations of the tunneling barrier are discussed. (C) 2003 American Institute of Physics.