The spin-coherent quantum transport through multiwall carbon nanotubes contacted by ferromagnetic Co pads is investigated experimentally. At 4.2 K, the devices show a remarkable increase of the magnetoresistance (MR) ratio with decreasing junction bias, reaching a maximum MR ratio of 30% at a junction bias current of 1 nA. The experimental results suggest the transport to be dominated by spin-dependent tunneling processes at the Co/nanotube interfaces and governed by the local magnetization. We also observe an asymmetry of the magnetoresistance peak position and width which is attributed to a local exchange biasing in the electrode material.

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We fabricated YBa2Cu3O7 (YBCO) direct current (dc) nano superconducting quantum interference devices (nanoSQUIDs) based on grain boundary Josephson junctions by focused ion beam patterning. Characterization of electric transport and noise properties at 4.2 K in magnetically shielded environment yields a very small inductance L of a few pH for an optimized device geometry. This in turn results in very low values of flux noise < 50 nΦ0/Hz 1/2 in the thermal white noise limit, which yields spin sensitivities of a few µB/Hz 1/2 (Φ0 is the magnetic flux quantum and µB is the Bohr magneton). We observe frequency-dependent excess noise up to 7 MHz, which can only partially be eliminated by bias reversal readout. This indicates the presence of fluctuators of unknown origin, possibly related to defect-induced spins in the SrTiO3 substrate. We demonstrate the potential of using YBCO nanoSQUIDs for the investigation of small spin systems, by placing a 39 nm diameter Fe nanowire, encapsulated in a carbon nanotube, on top of a non-optimized YBCO nanoSQUID and by measuring the magnetization reversal of the Fe nanowire via the change of magnetic flux coupled to the nanoSQUID. The measured flux signals upon magnetization reversal of the Fe nanowire are in very good agreement with estimated values, and the determined switching fields indicate magnetization reversal of the nanowire via curling mode.

The inflammatory and fibrotic intensity of a foreign body reaction largely depends on the porosity of the implanted material. Furthermore, the size of the pore and its geometry define the capability to allow tissue ingrowth. We present an image analysis system, which allows objectifying in two dimensions the pores' structure and geometry of textile fabrics, that are used to reinforce the abdominal wall or pelvic floor. The porosity of the textile is measured at four samples with differences in structure. The porosity decreases markedly if foreign body response is considered, leading to the definition of an "effective porosity". Because of the high stiffness of the polymer fibers the elasticity of textile implants usually result from a deformation of the pores, leading to a marked reduction of the effective porosity if a mechanical stress is applied. Further in vivo studies have to investigate, whether the preservation of a high effective porosity under stress may help to improve biocompatibility of textile implants.

Probes for magnetic force microscopy (MFM) were prepared by pinning iron-filled multiwall carbon nanotubes to conventional scanning force microscopy probes. These nanotube MFM probes reveal a great potential for high spatial resolution of both topography and magnetic stray field. The ends of the high aspect ratio iron nanowires within the nanotubes can be considered as stationary effective magnetic monopole moments which opens the possibility of quantitative stray field measurements in a straightforward manner. The carbon shells around the iron nanowires provide wear resistance and oxidation protection.

We report on the observation of spin-polarized tunneling magnetoresistance (TMR) in Co-contacted multiwalled carbon nanotubes (MWCNT). At 4.2 K, we find an increase of the TMR with decreasing junction bias. When the junction bias current is 0.5 nA, the highest value of −36% for the TMR ratio is found. The enhanced TMR ratio is explained by the onset of co-tunneling effects. We also find an asymmetric switching behavior which is tentatively attributed to an additional exchange biasing in the electrode material. For different samples, the TMR can assume both negative and positive values, indicating that the sign of the spin polarization of the tunneling electrons can be reversed. Apparently, the spin polarization sign depends sensitively on the detailed electronic configuration of the contact between Co and MWCNT.

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Iron-filled carbon nanotubes (Fe-CNTs) were used to prepare probes for magnetic force microscopy (MFM) by attaching them to the tips of conventional atomic force microscopy cantilevers. An optimized chemical vapor deposition process, employing a two stage furnace and ferrocene as a precursor, supplied the homogeneously filled Fe-CNTs required for the MFM probes. These can be regarded as cylindrically shaped single-domain nanomagnets that are protected from oxidation by a carbon shell. Carbon nanotubes are known to possess both great mechanical stability and elasticity, which lead to a much longer lifetime of these probes compared to conventional magnetically coated probes. It is shown that the prepared probes are suitable for magnetic imaging and so far show no sign of deterioration. Even very long nanotubes can be used as probes, which implies that they are extraordinarily stiff. It is also shown that attached Fe-CNTs can subsequently be tailored by electron-beam induced oxidation (e.g., to remove disturbing empty carbon shell parts) to better fit the requirements of an MFM tip.