255 research outputs found
Critical spin-flip scattering at the helimagnetic transition of MnSi
We report spherical neutron polarimetry (SNP) and discuss the spin-flip
scattering cross sections as well as the chiral fraction close to the
helimagnetic transition in MnSi. For our study, we have developed a
miniaturised SNP device that allows fast data collection when used in small
angle scattering geometry with an area detector. Critical spin-flip scattering
is found to be governed by chiral paramagnons that soften on a sphere in
momentum space. Carefully accounting for the incoherent spin-flip background,
we find that the resulting chiral fraction decreases gradually above the
helimagnetic transition reflecting a strongly renormalised chiral correlation
length with a temperature dependence in excellent quantitative agreement with
the Brazovskii theory for a fluctuation-induced first order transition.Comment: 5 pages, 3 figure
Low temperature magnetic structure of CeRhIn by neutron diffraction on absorption-optimized samples
Two aspects of the ambient pressure magnetic structure of heavy fermion
material CeRhIn have remained under some debate since its discovery:
whether the structure is indeed an incommensurate helix or a spin density wave,
and what is the precise magnitude of the ordered magnetic moment. By using a
single crystal sample optimized for hot neutrons to minimize neutron absorption
by Rh and In, here we report an ordered moment of . In
addition, by using spherical neutron polarimetry measurements on a similar
single crystal sample, we have confirmed the helical nature of the magnetic
structure, and identified a single chiral domain
Hybridization-Driven Orthorhombic Lattice Instability in URu2Si2
We have measured the elastic constant (C11-C12)/2 in URu2Si2 by means of
high-frequency ultrasonic measurements in pulsed magnetic fields H || [001] up
to 61.8 T in a wide temperature range from 1.5 to 116 K. We found a reduction
of (C11-C12)/2 that appears only in the temperature and magnetic field region
in which URu2Si2 exhibits a heavy-electron state and hidden-order. This change
in (C11-C12)/2 appears to be a response of the 5f-electrons to an orthorhombic
and volume conservative strain field \epsilon_xx-\epsilon_yy with
{\Gamma}3-symmetry. This lattice instability is likely related to a
symmetry-breaking band instability that arises due to the hybridization of the
localized f electrons with the conduction electrons, and is probably linked to
the hidden-order parameter of this compound.Comment: 5 pages, 4 figure
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