BaO has been introduced as a novel tunnel barrier material in magnetic tunnel junctions (MTJs). Due to the good agreement regarding lattice constants and crystal structure, we believe BaO to be particularly suitable as barrier in MTJs containing Heusler compound electrodes. Co 2 FeSi/BaO/Fe MTJs have been fabricated by molecular beam epitaxy (MBE) and investigated in terms of microstructure, transport properties and tunnel magneto resistance (TMR). A TMR amplitude as high as 104% at room temperature (RT) has been achieved for very small bias voltages ( V Bias ) and a strong dependence on V Bias could be observed as the TMR ratio decreases with increasing V Bias to about 14% at V Bias = 10 mV.

This paper highlights recent advances in synthesis and magnetotransport properties of magnetic Co nanopartides. It is shown that magnetic Co nanoparticles self-assembled in nanoparticular monolayers revealing giant magnetoresistance similar to granular systems but with additional features resulting from dipolar interactions between small domains of nanoparticles. A spin-valve with one magnetic Co nanoparticular electrode is employed as a model to demonstrate that individual magnetic moments of Co nanoparticles can be coupled to a magnetic Co layer which in turn offers tailoring of the resulting giant magnetoresistance characteristics. In addition, it is demonstrated that combining a magnetic on-off ratchet with magnetic tunneling junctions integrated in the ratchet introduces a new biosensor concept enabling: (1) simultaneous transporting and separating biomolecules, (2) dynamical biomolecule detection when passing magnetic tunneling junctions in a 1D arrangement. It is projected that this biosensor concept could be applied for viruses as well as for bacteria.

This article reviews recent developments on magnetoresistive detection of magnetic beads or nanoparticles by nanoscale sized sensors. Sensors are analyzed from an experimental and a numerical point of view in respect to their capability to either localize the position of a single magnetic particle or to detect the number of particles in a certain range. Guidelines are shown up on how to extend single sensors to sensor arrays with very high spatial resolution and how to modify the sensor shape in order to provide long distance measurements. Further, sensors in biological lab-on-a-chip environments are discussed. The magnetic ratchet and a gravitation based microfluidic component are reviewed as important tools to position and, therefore, detect biological components in continuous-flow devices.