79 research outputs found
Extended Magnetic Dome Induced by Low Pressures in Superconducting FeSeS
We report muon spin rotation (SR) and magnetization measurements under
pressure on FeSeS with x
.Above GPa we find microscopic coexistence of
superconductivity with an extended dome of long range magnetic order that spans
a pressure range between previously reported separated magnetic phases. The
magnetism initially competes on an atomic scale with the coexisting
superconductivity leading to a local maximum and minimum of the superconducting
. The maximum of corresponds to the onset of
magnetism while the minimum coincides with the pressure of strongest
competition. A shift of the maximum of for a series of single
crystals with x up to 0.14 roughly extrapolates to a putative magnetic and
superconducting state at ambient pressure for x .Comment: 10 pages, 6 figures, including supplemental materia
Gradual Enhancement of Stripe-Type Antiferromagnetism in Spin Ladder Material BaFeS Under Pressure
We report pressure-dependent neutron diffraction and muon spin
relaxation/rotation measurements combined with first-principles calculations to
investigate the structural, magnetic, and electronic properties of
BaFeS under pressure. The experimental results reveal a gradual
enhancement of the stripe-type ordering temperature with increasing pressure up
to 2.6 GPa and no observable change in the size of the ordered moment. The ab
initio calculations suggest that the magnetism is highly sensitive to the Fe-S
bond lengths and angles, clarifying discrepancies with previously published
results. In contrast to our experimental observations, the calculations predict
a monotonic reduction of the ordered moment with pressure. We suggest that the
robustness of the stripe-type antiferromagnetism is due to strong electron
correlations not fully considered in the calculations
Spin pseudogap in Ni-doped SrCuO2
The S=1/2 spin chain material SrCuO2 doped with 1% S=1 Ni-impurities is
studied by inelastic neutron scattering. At low temperatures, the spectrum
shows a pseudogap \Delta ~ 8 meV, absent in the parent compound, and not
related to any structural phase transition. The pseudogap is shown to be a
generic feature of quantum spin chains with dilute defects. A simple model
based on this idea quantitatively accounts for the exprimental data measured in
the temperature range 2-300 K, and allows to represent the momentum-integrated
dynamic structure factor in a universal scaling form.Comment: 5 pages, 3 figure
Universal fluctuating regime in triangular chromate antiferromagnets
We report x-ray diffraction, magnetic susceptibility, heat capacity, H
nuclear magnetic resonance (NMR), and muon spin relaxation (SR)
measurements, as well as density-functional band-structure calculations for the
frustrated triangular lattice Heisenberg antiferromagnet (TLHAF)
-HCrO (trigonal, space group: ). This compound
undergoes a clear magnetic transition at ~K, as seen
from the drop in the muon paramagnetic fraction and concurrent anomalies in the
magnetic susceptibility and specific heat. Local probes (NMR and SR)
reveal a broad regime with slow fluctuations down to , this
temperature corresponding to the maximum in the SR relaxation rate and in
the NMR wipe-out. From the comparison with NaCrO and -KCrO,
the fluctuating regime and slow dynamics below appear to be
hallmarks of the TLHAF with stacking that leads to a frustration of
interlayer couplings between the triangular planes. This interlayer frustration
is a powerful lever to generate spin states with persistent dynamics and may
bear implications to spin-liquid candidates with the triangular geometry.Comment: 14 pages, 11 figures, 2 table
Disordered ground state in the spin-orbit coupled Jeff = 1/2 distorted honeycomb magnet BiYbGeO5
We delineate quantum magnetism in the strongly spin-orbit coupled distorted honeycomb lattice antiferromagnet BiYbGeO5. Our magnetization and heat capacity measurements reveal that its low-temperature behavior is well described by an effective Jeff=12 Kramers doublet of Yb3+. The ground state is nonmagnetic with a tiny spin gap. Temperature-dependent magnetic susceptibility, magnetization isotherm, and heat capacity can be modeled well assuming isolated spin dimers with anisotropic exchange interactions JZ≃2.6 K and JXY≃1.3 K. Heat capacity measurements backed by muon spin relaxation suggest the absence of magnetic long-range order down to at least 80 mK both in zero field and in applied fields. This sets BiYbGeO5 apart from Yb2Si2O7, with its unusual regime of magnon Bose-Einstein condensation, and suggests negligible interdimer couplings, despite only a weak structural deformation of the honeycomb lattice
- …