An extremely sensitive miniature torque magnetometer using Si p-doped piezoresistive cantilevers is described. The magnetization m↘ of very small magnetic or superconducting samples (≤1 μg) deposited on the cantilever can be measured via the torque τ↘=m↘×B↘ produced on them by an applied field B. The high resolution in the lever deflection of the order of 0.1 Å corresponds to a torque sensitivity of the order of Δτ≂10−14 Nm. In a homogeneous field of 1 T this device allows magnetic moments as small as Δm≂10−14 Am2 to be measured, a value far smaller than that measurable by the best commercial superconducting quantum interference device magnetometers. Measurements performed on microcrystals of the high-Tc superconductors Bi2Sr2Ca1Cu2O8 and Hg1Ba2Ca3Cu4O10 in the static and dynamic modes demonstrate the excellent performance of this device at low temperature and in magnetic fields ranging between a few mT and 5 T.

We report on YBa2Cu3O7−δ thin-film preparation by a new laser deposition geometry, the so-called off-axis laser deposition. Combined with radiation-based substrate heating, this results in c-axis oriented, epitaxial YBa2Cu3O7−δ thin films with critical current densities above 106 A/cm2 at 77 K and zero field and an exceptionally good surface quality, with complete absence of the otherwise observed laser droplets. As proved by atomic force microscopy, the surface roughness is <80 Å over an area of at least 10×10 μm2. Using this off-axis geometry it is possible to coat both sides of a substrate simultaneously, providing a one-step process in double-sided thin-film deposition. Both YBa2Cu3O7−δ films on the substrate show identical superconducting properties.

Dedicated to Dr. Heinz Kimmel on the occasion of his 65th birthdayHost-guest chemistry is already widely used for the detection of ions['* 2] with suitable electrodes[31 and especially with the ion-sensitive field-effect transistor (ISFET)l3], a high selectivity being achieved in this way. These methods of molecular recognition are also well known for the inclusion of neutral molecules[4] by hosts in water. Only a few sensor applications exist in this field. The reason for this are the problems with the mass-sensitive devices,15] namely the quartz microbalance (QMB) and the more sensitive surfaceacoustic-wave oscillator (SAW). The oscillations of these elements are strongly damped in liquids and therefore a special type of elastic waves have to be used.[61 More favorable conditions, however, exist for the detection of gases and vapors using these mass-sensitive devices, and many examples of pure absorption processes have been reported, ['] although there are only a few reports about chemical reactions[*] and especially molecular recognitionL9, ' ' 1 being applied as the sensor phenomena. Shape recognition of the analyte can be achieved if the guest is included within the cavity of the host and not purely absorbed outside the hole. This strategy can lead to a high selectivity in analogy to the extremely specific but chemically unstable biosen~ors [~] where enzymes are the sensitive material.It is possible to decide whether the principles of host-guest chemistry are applicable for the detection of vaporous ana-