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Biomedical subjects

H J Hug

Publications and source records attributed to H J Hug.

6 recordsLinked to original sources
PubMed2006

Remanence due to wall magnetization and counterintuitive magnetometry data in 200-nm films of Ni.

200-nm-thick Ni films in an epitaxial Cu/Ni/Cu/Si(001) structure are expected to have an in-plane effective magnetic anisotropy. However, the in-plane remanence is only 42%, and magnetic force microscopy domain images suggest perpendicular magnetization. Quantitative magnetic force microscopy analysis can resolve the inconsistencies and show that (i) the films have perpendicular domains capped by closure domains with magnetization canted at 51 degrees from the film normal, (ii) the magnetization in the Bloch domain walls between the perpendicular domains accounts for the low in-plane remanence, and (iii) the perpendicular magnetization process requires a short-range domain wall motion prior to wall-magnetization rotation and is nonhysteretic, whereas the in-plane magnetization requires long-range motion before domain-magnetization rotation and is hysteretic.

Journal Article↗
PubMed2006

Ultrastructural appearance of embedded and polished wood cell walls as revealed by Atomic Force Microscopy.

Atomic Force Microscopy (AFM) was used to investigate the ultrastructural appearance of transverse wood cell wall surfaces in embedded and polished Norway spruce wood blocks. The prepared surfaces showed only little height differences, suitable for high resolution AFM phase contrast imaging. Our results revealed randomly arranged wood cell wall components in the thick secondary 2 (S2) layers of the tracheid cell walls. It is concluded that the observed distribution pattern of the cellulose fibril/matrix structure is close to the original cell wall structure. In this context, the plasticity of wood cell wall components to re-arrange and adjust to different conditions resulting in diverse structural pattern is discussed.

Cell Wall↗
PubMed2004

Sublattice identification in scanning force microscopy on alkali halide surfaces.

We propose and apply to the KBr(001) surface a new procedure for species recognition in scanning force microscopy (SFM) of ionic crystal surfaces which show a high symmetry of the charge arrangement. The method is based on a comparison between atomistic simulations and site-specific frequency versus distance measurements. First, by taking the difference of force-distance curves extracted at a few judiciously chosen surface sites we eliminate site-independent long-range forces. The obtained short-range force differences are then compared with calculated ones assuming plausible tip apex models. This procedure allows for the first time identification of the tip apex polarity and of the positive and negative sublattices in SFM images of the (001) cleavage surface of an ionic crystal with the rock salt structure.

Journal Article↗
PubMed2003

Direct imaging and determination of the uncompensated spin density in exchange-biased CoO/(CoPt) multilayers.

Magnetic force microscopy (MFM) measurements were performed on an exchange-biased CoO/(CoPt) multilayer sample at 7.5 K. Applying an external magnetic field of up to 7 T saturates the ferromagnetic layer and the remaining uncompensated antiferromagnetic spins at the antiferromagnet-ferromagnet interfaces are imaged with high lateral resolution. The coupling between the uncompensated spins and the spins in the ferromagnet are found to be antiferromagnetic. Quantitative analysis of the MFM images revealed that 7% of the spins at the interface are uncompensated and contribute to the exchange biasing.

Journal Article↗
PubMed2001

Quantitative measurement of short-range chemical bonding forces.

We report direct force measurements of the formation of a chemical bond. The experiments were performed using a low-temperature atomic force microscope, a silicon tip, and a silicon (111) 7x7 surface. The measured site-dependent attractive short-range force, which attains a maximum value of 2.1 nanonewtons, is in good agreement with first-principles calculations of an incipient covalent bond in an analogous model system. The resolution was sufficient to distinguish differences in the interaction potential between inequivalent adatoms, demonstrating the ability of atomic force microscopy to provide quantitative, atomic-scale information on surface chemical reactivity.

Journal Article↗