New materials and applications for magnetic tunnel junctions

Large opportunities in magnetolectronic devices are opened by the spin dependent tunnelling resistance, where a strong dependence of the tunnelling current on an external magnetic field can be found. Within a short time, the quality of the junctions increased dramatically. We will briefly address some important basics depending on the material stacking sequence of the underlying thin film system with special regard to the ferromagnetic electrodes. Scaling issues, i.e. the influence of the geometry of small tunnelling junctions especially on the magnetic switching behaviour are considered down to junction sizes below 0.01 μm2. The last part will give a short overview on applications beyond the use of the tunnelling elements as storage cells in MRAMs. This concerns mainly field programmable logic circuits, where we demonstrate the clocked operation of a programmed AND gate. The second ‘unconventional’ feature is the use as sensing elements in DNA or protein biochips, where molecules marked magnetically with commercial beads can be detected via the dipole stray field in a highly sensitive and relatively simple way. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)