Volume 85, Issue 4, 15 February 1999
Index of content:
85(1999); http://dx.doi.org/10.1063/1.369565View Description Hide Description
Minor addition of Cu to melt-spun alloy is effective on reducing the grain size of the nanocompositepermanent magnet produced via the crystallization route from the amorphous phase, thereby improving hard magnetic properties. Three-dimensional atom probe and transmission electron microscopy observations have shown that Cu clusters with a number density of is formed prior to the nucleation event of the primary crystal. In the nucleation and growth stage of the primary crystals, Cu clusters are in direct contact with the primary particles, suggesting that Cu clusters serve as heterogeneous nucleation sites for the primary particles, thereby increasing the number density of the particles.
85(1999); http://dx.doi.org/10.1063/1.369566View Description Hide Description
We report static pressure compression of cerium metal to 208 GPa (volume compression in a diamond anvil cell at room temperature. Cerium is unique in the elements because of proximity of the f shell to the Fermi energy and related phase transformations induced by pressure. The energy-dispersive x-ray diffraction studies were carried out on cerium metal to 208 GPa using a synchrotron x-ray source and an internal copperpressure standard. A collapsed body centered tetragonal phase is found to be stable to the highest pressure with axial ratio remarkably constant at 1.680±0.006 in the 90–208 GPa pressure range in excellent agreement with theory. Cerium is thus isostructural and isoelectronic with -band metal thorium at ultrapressures. We present equation of state parameters, which describe the compression of cerium to ultrapressures.
85(1999); http://dx.doi.org/10.1063/1.369567View Description Hide Description
Coupled arrays of vertical cavity surface emitting lasers with controlled optical disorder were realized by patterning the reflectivity of the top cavitymirrors. The size of each square array element, defined by photolithography, determines the local cavity oscillation frequency and loss. Optical disorder across the array can therefore be introduced by varying the size of the lasing elements. The localization of photon modes and the array coherence were investigated as a function of the degree of disorder and the array dimensionality. We found that a higher degree of disorder leads to more localized coherent modes and consequently to broader far-field patterns. However, the effects of disorder reduce considerably as the array dimensionality increases from one to two by adding array rows, leading to more effective suppression of mode localization.