116 research outputs found
Effect of Applied Orthorhombic Lattice Distortion on the Antiferromagnetic Phase of CeAuSb
We study the response of the antiferromagnetism of CeAuSb to orthorhombic
lattice distortion applied through in-plane uniaxial pressure. The response to
pressure applied along a lattice direction shows a
first-order transition at zero pressure, which shows that the magnetic order
lifts the symmetry of the unstressed lattice. Sufficient
pressure appears to rotate the principal axes of the
order from to . At low pressure, the transition at is weakly first-order, however it
becomes continuous above a threshold pressure. We discuss
the possibility that this behavior is driven by order parameter fluctuations,
with the restoration of a continuous transition a result of reducing the
point-group symmetry of the lattice.Comment: 6 pages, 7 figure
Piezoelectric-based apparatus for strain tuning
We report the design and construction of piezoelectric-based apparatus for
applying continuously tuneable compressive and tensile strains to test samples.
It can be used across a wide temperature range, including cryogenic
temperatures. The achievable strain is large, so far up to 0.23% at cryogenic
temperatures. The apparatus is compact and compatible with a wide variety of
experimental probes. In addition, we present a method for mounting
high-aspect-ratio samples in order to achieve high strain homogeneity.Comment: 8 pages, 8 figure
Even odder after twenty-three years : the superconducting order parameter puzzle of Sr2RuO4
Funding: Max Planck Society.In this short review, we aim to provide a topical update on the status of efforts to understand the superconductivity of Sr2RuO4. We concentrate on the quest to identify a superconducting order parameter symmetry that is compatible with all the major pieces of experimental knowledge of the material, and highlight some major discrepancies that have become even clearer in recent years. As the pun in the title suggests, we have tried to start the discussion from scratch, making no assumptions even about fundamental issues such as the parity of the superconducting state. We conclude that no consensus is currently achievable in Sr2RuO4, and that the reasons for this go to the heart of how well some of the key probes of unconventional superconductivity are really understood. This is therefore a puzzle that merits continued in-depth study.Publisher PDFPeer reviewe
Effect of uniaxial stress on the magnetic phases of CeAuSb
We present results of measurements of resistivity of \CAS{} under the
combination of -axis magnetic field and in-plane uniaxial stress. In
unstressed \CAS{} there are two magnetic phases. The low-field A phase is a
single-component spin-density wave (SDW), with , and the high-field B phase consists of microscopically coexisting
and spin-density waves. Pressure along
a lattice direction is a transverse field to both of
these phases, and so initially has little effect, however eventually induces
new low- and high-field phases in which the principal axes of the SDW
components appear to have rotated to the directions.
Under this strong compression, the field evolution of the
resistivity is much smoother than at zero strain: In zero strain, there is a
strong first-order transition, while under strong it
becomes much broader. We hypothesize that this is a consequence of the uniaxial
stress lifting the degeneracy between the (100) and (010) directions.Comment: 8 pages, 7 figure
A Terraced Scanning Superconducting Quantum Interference Device Susceptometer with Sub-Micron Pickup Loops
Superconducting Quantum Interference Devices (SQUIDs) can have excellent spin
sensitivity depending on their magnetic flux noise, pick-up loop diameter, and
distance from the sample. We report a family of scanning SQUID susceptometers
with terraced tips that position the pick-up loops 300 nm from the sample. The
600 nm - 2 um pickup loops, defined by focused ion beam, are integrated into a
12-layer optical lithography process allowing flux-locked feedback, in situ
background subtraction and optimized flux noise. These features enable a
sensitivity of ~70 electron spins per root Hertz at 4K.Comment: See http://stanford.edu/group/moler/publications.html for an
auxiliary document containing additional fabrication details and discussio
Limits on Superconductivity-Related Magnetization in SrRuO and PrOsSb from Scanning SQUID Microscopy
We present scanning SQUID microscopy data on the superconductors Sr2RuO4 (Tc
= 1.5 K) and PrOsSb (Tc = 1.8 K). In both of these materials,
superconductivity-related time-reversal symmetry-breaking fields have been
observed by muon spin rotation; our aim was to visualize the structure of these
fields. However in neither SrRuO nor PrOsSb do we observe
spontaneous superconductivity-related magnetization. In SrRuO, many
experimental results have been interpreted on the basis of a
superconducting order parameter. This order parameter is expected to give
spontaneous magnetic induction at sample edges and order parameter domain
walls. Supposing large domains, our data restrict domain wall and edge fields
to no more than ~0.1% and ~0.2% of the expected magnitude, respectively.
Alternatively, if the magnetization is of the expected order, the typical
domain size is limited to ~30 nm for random domains, or ~500 nm for periodic
domains.Comment: 8 pages, 7 figures. Submitted to Phys. Rev.
A new stress dilatometer and measurement of the thermal expansion under uniaxial stress of MnSn
We present a method for measuring thermal expansion under tunable uniaxial
stresses, and show measurements of the thermal expansion of MnSn, a room
temperature antiferromagnet that exhibits a spontaneous Hall effect, under
uniaxial stresses of up to 1.51 GPa compression. Measurement of thermal
expansion provides thermodynamic data about the nature of phase transitions,
and uniaxial stress provides a powerful tuning method that does not introduce
disorder. MnSn exhibits an anomaly in its thermal expansion near 270
K, associated with a first-order change in its magnetic structure. We show this
transition temperature is suppressed by 54.6 K by 1.51 GPa compression along
[0001]. We find the associated entropy change at the transition to be
0.1 J mol K and to vary only weakly with applied stress
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