5 research outputs found
Classical spin liquid or extended critical range in h-YMnO?
Inelastic neutron experiments on the classical triangular-lattice
geometrically frustrated antiferromagnet h-YMnO reveal diffuse, gapless
magnetic excitations present both below and far above the ordering temperature,
. The correlation length of the excitations increases as the temperature
approaches zero, bearing strong resemblance to critical scattering. We model
the scattering as critical spin-spin correlations in a two-dimensional magnetic
ground state, and we speculate that this may provide a general framework to
understand features typically attributed to classical spin liquids
Gradual emergence of superconductivity in underdoped LSCO
We present triple-axis neutron scattering studies of low-energy magnetic
fluctuations in strongly underdoped LaSrCuO with ,
and , providing quantitative evidence for a direct competition
between these fluctuations and superconductivity. At dopings and
, three-dimensional superconductivity is found, while only a very weak
signature of two-dimensional superconductivity residing in the CuO planes
is detectable for . We find a surprising suppression of the low-energy
fluctuations by an external magnetic field at all three dopings. This implies
that the response of two-dimensional superconductivity to a magnetic field is
similar to that of a bulk superconductor. Our results provide direct evidence
of a very gradual onset of superconductivity in cuprates.Comment: 5 pages, 4 figures, and supplementary materia
Magnetic structure and dynamics of cuprate superconductors studied by neutron scattering
Multiple scattering camouflaged as magnetic stripes in single crystals of superconducting (La,Sr)2CuO4
Neutron diffraction has been a very prominent tool to investigate
high-temperature superconductors, in particular through the discovery of an
incommensurate magnetic signal known as stripes. We here report the findings of
a neutron diffraction experiment on the superconductor (La,Sr)CuO,
where a spurious signal appeared to be magnetic stripes. The signal strength
was found to be strongly dependent on the neutron energy, peaking at ~meV. We therefore attribute the origin of this signal to be a combination
of multiple scattering and crystal twinning. A forward calculation of the
scattering intensity including these two effects almost completely recovers our
experimental observations. We emphasise the need for employing such analysis
when searching for ways to avoid spurious scattering signals.Comment: 8 pages, 5 figure
Non-destructive characterisation of dopant spatial distribution in cuprate superconductors
Proper characterisation of investigated samples is vital when studying
superconductivity as impurities and doping inhomogeneities can affect the
physical properties of the measured system. We present a method where a
polarised neutron imaging setup utilises the precession of spin-polarised
neutrons in the presence of a trapped field in the superconducting sample to
spatially map out the critical temperature for the phase transition between
superconducting and non-superconducting states. We demonstrate this method on a
superconducting crystal of the prototypical high-temperature superconductor
(La,Sr)CuO. The results, which are backed up by complementary magnetic
susceptibility measurements, show that the method is able to resolve minor
variations in the transition temperature across the length of the LSCO crystal,
caused by inhomogeneities in strontium doping.Comment: 11 pages, 7 figure