179 research outputs found
Polarized beam operation of the Hybrid Spectrometer at the pulsed Spallation Neutron Source
The concept of a neutron Hybrid Spectrometer (HYSPEC) combines the
time-of-flight spectroscopy with the focusing Bragg optics and incorporates a
polarized beam option. Here we describe the polarization analysis scheme
proposed for HYSPEC and quantify its performance via the Monte-Carlo
simulations. We find that the broadband supermirror-bender transmission
polarizers provide reasonably good polarization analysis capability within
about 8-10 meV energy window for scattered neutron energies in the thermal
range up to about 25 meV.Comment: Preprint, to appear in Physica B. 10 pages, 4 figure
Novel magnetic phase in a weakly ordered spin-1/2 chain antiferromagnet SrCuO
We present the magnetic phase diagram of a spin-1/2 chain antiferromagnet
SrCuO studied by ultrasound phase-sensitive detection technique. We
observe an enhanced effect of external magnetic field on the ordering
temperature of the system, which is in the extreme proximity to the quantum
critical point. Inside the N\'eel ordered phase, we detect an additional
field-induced continuous phase transition, which is unexpected for a collinear
Heisenberg antiferromagnet. This transition is accompanied by softening of
magnetic excitation mode observed by electron-spin resonance, which can be
associated with a longitudinal (amplitude) mode of the order parameter in a
weakly-coupled system of spin-1/2 chains. These results suggest transition from
a transverse collinear antiferromagnet to an amplitude-modulated spin density
wave phase induced by magnetic field.Comment: 4 pages, 4 figure
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