62 research outputs found
Microscopic and Macroscopic Signatures of Antiferromagnetic Domain Walls
Magnetotransport measurements on small single crystals of Cr, the elemental
antiferromagnet, reveal the hysteretic thermodynamics of the domain structure.
The temperature dependence of the transport coefficients is directly correlated
with the real-space evolution of the domain configuration as recorded by x-ray
microprobe imaging, revealing the effect of antiferromagnetic domain walls on
electron transport. A single antiferromagnetic domain wall interface resistance
is deduced to be of order at a
temperature of 100 K.Comment: 3 color figure
Collective pinning dynamics of charge-density waves in 1T-TaS 2
Using high-resolution x-ray scattering and x-ray photon correlation spectroscopy (XPCS), we have investigated the structure and dynamics of charge density wave (CDW) dynamics in pure and titanium-doped 1T-TaS 2. Time-averaged scattering measurements of pure and doped samples reveal that 1T-TaS 2 is a weakly pinned two-dimensional CDW system. Using XPCS, we find that after long anneals the CDW domain structure in the incommensurate phase is pinned and stable against spontaneous fluctuations thus rejecting phasons as spontaneous excitations in higher-dimensional CDW systems. By examining the dynamics of deeply quenched samples upon heating, we find that metastable CDW configurations collectively rearrange in a nonequilibrium manner. For nominally pure samples, we determine an energy barrier to relaxation of 4600 K that is considerably greater than that found for lower-dimensional CDW
Surface Induced Order in Liquid Metals and Binary Alloys
Measurements of the surface x-ray scattering from several pure liquid metals
(Hg, Ga, and In) and from three alloys (Ga-Bi, Bi-In, and K-Na) with different
heteroatomic chemical interactions in the bulk phase are reviewed.
Surface-induced layering is found for each elemental liquid metal. The surface
structure of the K-Na alloy resembles that of an elemental liquid metal. Bi-In
displays pair formation at the surface. Surface segregation and a wetting film
are found for Ga-Bi.Comment: 10 pages, 3 fig, published in Journal of Physics: Condensed Matte
Recommended from our members
Wetting Behavior at the Free Surface of a Liquid Gallium–Bismuth Alloy: An X-ray Reflectivity Study Close to the Bulk Monotectic Point
We present X-ray reflectivity measurements from the free surface of a liquid gallium–bismuth alloy (Ga–Bi) in the temperature range close to the bulk monotectic temperature =222C. Our measurements indicate a continuous formation of a thick wetting film at the free surface of the binary system driven by the first order transition in the bulk at the monotectic point. We show that the behavior observed is that of a complete wetting at a tetra point of solid–liquid–liquid–vapor coexistence.Engineering and Applied Science
Solvent Mediated Assembly of Nanoparticles Confined in Mesoporous Alumina
The controlled self-assembly of thiol stabilized gold nanocrystals in a
mediating solvent and confined within mesoporous alumina was probed in situ
with small angle x-ray scattering. The evolution of the self-assembly process
was controlled reversibly via regulated changes in the amount of solvent
condensed from an undersaturated vapor. Analysis indicated that the
nanoparticles self-assembled into cylindrical monolayers within the porous
template. Nanoparticle nearest-neighbor separation within the monolayer
increased and the ordering decreased with the controlled addition of solvent.
The process was reversible with the removal of solvent. Isotropic clusters of
nanoparticles were also observed to form temporarily during desorption of the
liquid solvent and disappeared upon complete removal of liquid. Measurements of
the absorption and desorption of the solvent showed strong hysteresis upon
thermal cycling. In addition, the capillary filling transition for the solvent
in the nanoparticle-doped pores was shifted to larger chemical potential,
relative to the liquid/vapor coexistence, by a factor of 4 as compared to the
expected value for the same system without nanoparticles.Comment: 9 pages, 9 figures, appeared in Phys. Rev.
Capillary Filling of Anodized Alumina Nanopore Arrays
The filling behavior of a room temperature solvent,
perfluoromethylcyclohexane, in approximately 20 nm nanoporous alumina membranes
was investigated in situ with small angle x-ray scattering. Adsorption in the
pores was controlled reversibly by varying the chemical potential between the
sample and a liquid reservoir via a thermal offset, T. The system
exhibited a pronounced hysteretic capillary filling transition as liquid was
condensed into the nanopores. These results are compared with Kelvin-Cohan
theory, with a modified Derjaguin approximation, as well as with predictions by
Cole and Saam.Comment: 4 pages, 3 figures, pre-proof
- …