In suitably designed mesoscopic semiconductor structures, the phenomenon of ballistic rectification can be observed. A currently discussed microscopic model relates the observations to the interplay between fully quantized and quasiclassical current paths. We present measurements that contribute substantially to the clarification of the fascinating topic. In particular, we observe the opposite sign of the output voltage as compared to the prediction. Demonstrating the basic principle upon which the rectification is based--the asymmetry of the voltage drop in a quasiclassical wire--and extending the model to the classical transport regime, we can well explain our experiments as being caused by the interplay of quasiclassical ballistic and classical transport. Tunable ballistic rectifiers generating very large output signals and operating at room temperature raise the hope for future applications.

Abstmct. ---In this work an evaluation tool for the chamcterization of high-density recording thin film media is discussed. The measurement principles are based on the anomalous and the planar Hall effect. We used these Hall effects to chamcterize ferromagnetic Co-Cr films and Co/Pd mulitlayers having perpendicular anisotropy. The measurement set-up that was built has a sensitivity capable of measuring the hysteresis loops of O.2xO.2 ~m2 Hall structures in Co-Cr and jumps were observed in the Hall voltage as a function of the applied field. Easy-axis measurements have been carried out, but the results are not in complete agreement with conventional techniques. A thickness series of Co/Pd multilayers has been chamcterized with the planar Hall effect imd the magnetoresistance mtio.

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ABSTRACT. In this article we investigate points of contact between micro-electromechanical systems (MEMS) and nanotechnology. Several examples of companies harnessing nanoelectromechanical systems (NEMS) are presented, highlighting the fields in which a downscaling of MEMS will become commercially important. Although major MEMS companies do not feel concerned with nanotechnology, NEMS are likely to have an impact on mass markets in the fields of storage, sensing, radio frequency (RF) MEMS, and systems based on carbon nanotubes (CNTs). Nanotechnology Perceptions 2 (2006) 267-275Nonsubscribers: purchase individual article

The magnetization reversal of Co–Cr with perpendicular anisotropy is studied by anomalous Hall effect measurements and by micromagnetic simulations. In a measured hysteresis loop of a 300 nm×300 nm sample (consisting of approximately 40 columns of Co–Cr), discrete jumps are observed, together with a more or less continuous change in magnetization, the latter with both positive and negative sign. The continuous and discrete parts of the hysteresis loop are separated to extract micromagnetic information from the anomalous Hall measurement. The discrete jumps are attributed to parts of columns that switch irreversibly, the continuous magnetization change is attributed to reversible rotation, partly of volumes with in-plane anisotropy. These assumptions are checked by means of a micromagnetic model.