Book Review: Antarctic Seals: Research Methods and Techniques

Book Title: Antarctic Seals: Research Methods and TechniquesBook Author: Edited by R.M. LawsCambridge University Press 1993. ISBN 0-521-44302-4. 390 pp

Notes on two brief surveys of the small mammal fauna on the Rooiberg, Ladismith, southern Cape Province

Two brief (3½ days each) trapping surveys of the small mammal fauna in fynbos vegetation on the Rooiberg mountains were conducted at the beginning and end of the rodent breeding season in 1978. Four study areas were selected at different altitudes and in different vegetation types. A total of six rodent, three shrew and one small carnivore species were captured. Estimates of density and biomass are given and were found to be relatively high for fynbos communities at the end of the breeding season (March). Differences were found between the fauna inhabiting north-facing and south-facing slopes

A vagrant Subantarctìc fur seal Arctocephalus tropicalis found in the Comores

A juvenile Subantarctic fur seal, Arctocephalus tropicalis was caught near the island of Anjouan, Comores, about 500 km off the east coast of Africa, on 20 August 1990. This record represents a northerly extension by some 1800 km of the recorded east coast range. The breeding colonies of this species are on temperate islands north of the Antarctic Polar Front. The dosest colonies are on Amsterdam Island and the Prince Edward islands, nearly 4000 km south-west and south, respectively of this sighting

Out-of-plane magnetic domain structure in a thin film of La0.67Sr0.33MnO3 on SrTiO3 (001) observed by magnetic force microscopy

The room temperature out-of-plane magnetization of epitaxial thin films of La0.67Sr0.33MnO3 on SrTiO3 (001) has been investigated with magnetic force microscopy, using magnetic tips with very small coercivity, relative to the film. A clear magnetic pattern in the form of a checkerboard, with domain dimensions of a few hundred nanometers, was found for the thin, coherently strained films, which is approximately aligned along the maximum strain [110] and [1[overline 1]0] directions in the film. With increasing in-plane applied magnetic field, the magnetic contrast reduces, reflecting the rotation of the magnetization vector into the plane of the film. This process is reversible with the field. The out-of-plane magnetic pattern is not sensitive to rotation of the in-plane field. We attribute the observed out-of-plane magnetization component to an out-of-plane magnetic anisotropy, which is a remainder of the [111] magnetic easy axis in bulk La0.67Sr0.33MnO3 single crystal

Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth

During the initial growth of the ferromagnetic oxide SrRuO3 on TiO2-terminated SrTiO3, we observe a self-organized conversion of the terminating atomic layer from RuO2 to SrO. This conversion induces an abrupt change in growth mode from layer by layer to growth by step advancement, indicating a large enhancement of the surface diffusivity. This growth mode enables the growth of single-crystalline and single-domain thin films. Both conversion and the resulting growth mode enable the control of the interface properties in heteroepitaxial multilayer structures on an atomic level

Growth mode transition from layer-by-layer to step-flow during the growth of heteroepitaxial SrRu)3 on (001) SrTiO3

We have observed the growth mode transition from two-dimensional (2D) layer-by-layer to step-flow in the earliest stage growth of heteroepitaxial SrRuO3 thin films on TiO2-terminated (001) SrTiO3 substrates by in situ high pressure reflective high energy electron diffraction (RHEED) and atomic-force microscopy. There is no RHEED intensity recovery after each laser pulse in the first oscillation when the growth mode is 2D layer-by-layer. On the other hand, it is getting more pronounced in the second oscillation, and finally reaches a dynamic steady state in which the growth mode is completely changed into the step-flow mode. The origin of the growth mode transition can be attributed to a change in the mobility of adatoms and switching the surface termination layer from the substrate to the film. SrRuO3 thin films with an atomically smooth surface grown by atomic layer control can be used in oxide multilayered heterostructure devices

Magnetization reversal mechanism in La0.67Sr0.33MnO3 thin films on NdGaO3 substrates

The field angle dependence of the coercive field of La0.67Sr0.33MnO3 thin films grown epitaxially on NdGaO3 substrates with different crystallographic orientations was determined. All films show uniaxial anisotropy. The angle dependence of the coercivity is best described by a two-phase model, explaining the strong increase in the coercive field for increasing field angles, away from the easy axis direction, as well as the sharp decrease for angles close to the hard direction. This implies that magnetization reversal starts with the depinning of domain walls, analogous to the Kondorsky model. With increasing field the reversal in the domains is not abrupt, but is determined by the gradual displacement of the domain walls. These results are of significance for understanding and possibly engineering of the switching behavior of magnetic tunnel junctions