19,597 research outputs found
Magnetic Susceptibility of Collinear and Noncollinear Heisenberg Antiferromagnets
Predictions of the anisotropic magnetic susceptibility chi below the
antiferromagnetic (AFM) ordering temperatures TN of local moment Heisenberg
AFMs have been made previously using molecular field theory (MFT) but are very
limited in their applicability. Here a MFT calculation of chi(T<=TN) is
presented for a wide variety of collinear and noncollinear Heisenberg AFMs
containing identical crystallographically equivalent spins without recourse to
magnetic sublattices. The results are expressed in terms of directly measurable
experimental parameters and are fitted with no adjustable parameters to
experimental chi(T<=TN) data from the literature for several collinear and
noncollinear AFMs. The influence of spin correlations and fluctuations beyond
MFT is quantified by the deviation of the theory from the data. The origin of
the universal chi(T<=TN) observed for triangular lattice AFMs exhibiting
coplanar noncollinear 120 degree AFM ordering is clarified.Comment: 5 pages, 5 figure
Crossover Between Weakly and Strongly Self-avoiding Random Surfaces
We investigate the crossover between weak and strong self-avoidance in a
simulation of random surfaces with extrinsic curvature. We consider both
dynamically triangulated and rigid surfaces with the two possible
discretizations of the extrinsic curvature term.Comment: 5 page
Synchronized voltage contrast display analysis system
An apparatus and method for comparing internal voltage potentials of first and second operating electronic components such as large scale integrated circuits (LSI's) in which voltage differentials are visually identified via an appropriate display means are described. More particularly, in a first embodiment of the invention a first and second scanning electron microscope (SEM) are configured to scan a first and second operating electronic component respectively. The scan pattern of the second SEM is synchronized to that of the first SEM so that both simultaneously scan corresponding portions of the two operating electronic components. Video signals from each SEM corresponding to secondary electron signals generated as a result of a primary electron beam intersecting each operating electronic component in accordance with a predetermined scan pattern are provided to a video mixer and color encoder
Spin dynamics in hole-doped two-dimensional S=1/2 Heisenberg antiferromagnets: ^{63}Cu NQR relaxation in La_{2-x}Sr_xCuO_4 for
The effects on the correlated Cu^{2+} S = 1/2 spin dynamics in the
paramagnetic phase of La_{2-x}Sr_xCuO_4 (for ) due to the
injection of holes are studied by means of ^{63}Cu NQR spin-lattice relaxation
time T_1 measurements. The results are discussed in the framework of the
connection between T_1 and the in-plane magnetic correlation length
. It is found that at high temperatures the system remains in
the renormalized classical regime, with a spin stiffness constant
reduced by small doping to an extent larger than the one due to Zn doping. For
the effect of doping on appears to level off. The
values for derived from T_1 for K are much larger
than the ones estimated from the temperature behavior of sublattice
magnetization in the ordered phase (). It is argued that these
features are consistent with the hypothesis of formation of stripes of
microsegregated holes.Comment: 10 pages, 3 figure
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