Interaction effects and transport properties of Pt capped Co nanoparticles

We studied the magnetic and transport properties of Co nanoparticles (NPs) being capped with varying amounts of Pt. Beside field and temperature dependent magnetization measurements we performed delta-M measurements to study the magnetic interactions between the Co NPs. We observe a transition from demagnetizing towards magnetizing interactions between the particles for an increasing amount of Pt capping. Resistivity measurements show a crossover from giant magnetoresistance towards anisotropic magnetoresistance

Effect of a Magnetic Field on the Dipole Echo in Glasses with Nuclear Quadrupole Moments

The effect of a magnetic field on the dipole echo amplitude in glasses at temperatures of about 10 mK caused by nonspherical nuclei with electric quadrupole moments has been studied theoretically. It has been shown that in this case, the two-level systems (TLS's) that determine the glass properties at low temperatures are transformed into more complicated multilevel systems. These systems have new properties as compared to usual TLS's and, in particular, exhibit oscillations of electric dipole echo amplitude in magnetic field. A general formula that describes the echo amplitude in an arbitrary split TLS has been derived with perturbation theory. Detailed analytic and numerical analysis of the formula has been performed. The theory agrees qualitatively and quantitatively well with experimental data.Comment: 5 pages, 3 figure

Large antenna apertures and arrays for deep space communications

Effect of frequency on communications capability, single antennas and arrays, and economic balance between ground station and spacecraft developmen

Telegraph Noise in Coupled Quantum Dot Circuits Induced by a Quantum Point Contact

Charge detection utilizing a highly biased quantum point contact has become the most effective probe for studying few electron quantum dot circuits. Measurements on double and triple quantum dot circuits is performed to clarify a back action role of charge sensing on the confined electrons. The quantum point contact triggers inelastic transitions, which occur quite generally. Under specific device and measurement conditions these transitions manifest themselves as bounded regimes of telegraph noise within a stability diagram. A nonequilibrium transition from artificial atomic to molecular behavior is identified. Consequences for quantum information applications are discussed.Comment: 4 pages, 3 figures (as published