183 research outputs found
Magnetic domain depinning as possible evidence for two ferromagnetic phases in LaCrGe
Two ferromagnetic phases, FM1 and FM2, were first proposed to exist in
LaCrGe based on a broad maximum in the temperature derivative of
resistivity resembling that of the superconducting ferromagnet UGe where
FM1 and FM2 are well-established. While evidence for two FM phases can be found
in certain additional probes, corresponding anomalies in magnetization have not
been recognized until now. Our spatially-resolved images of the magnetic
domains show a substantial change in the domain structure between the higher
temperature FM1 phase and the lower temperature FM2 phase. Furthermore, our
measurements of the coercive field and virgin magnetization curves reveal an
unconventional magnetic domain pinning region in the FM1 phase, followed by a
depinning region at lower temperatures where the system is reported to
crossover into the FM2 phase. We incorporate this discovery into a simple
domain magnetization model that demystifies the magnetization curve seen in all
previous studies. Finally, we find that the unusual domain behavior can be
explained by a change in the ferromagnetic exchange interaction and magnetic
moment, both of which are consistent with the existence of two FM phases. This
revelation may help explain a range of anomalous behaviors observed in
LaCrGe and rekindles the discussion about the prevalence of multiple FM
phases in fragile FM systems.Comment: 7+8 pages, 4+8 figures. Revised with suggestions from refere
Topological surface states above the Fermi energy in
We report a detailed experimental study of the band structure of the recently
discovered topological material . Using
the combination of scanning tunneling spectroscopy and angle-resolved
photo-emission spectroscopy with surface K-doping, we probe the band structure
of with energy and momentum resolution
above the Fermi level. Our experiments show the presence of multiple surface
states with a linear Dirac-like dispersion, consistent with the predictions
from previously reported band structure calculations. In particular, scanning
tunneling spectroscopy measurements provide the first experimental evidence for
the strong topological surface state predicted at 460 meV, which stems from the
band inversion between Hf-d and Te-p orbitals. This band inversion comprised of
more localized d-states could result in a better surface-to-bulk conductance
ratio relative to more traditional topological insulators.Comment: Supplementary materials available upon reques
Long range order and two-fluid behavior in heavy electron materials
The heavy electron Kondo liquid is an emergent state of condensed matter that
displays universal behavior independent of material details. Properties of the
heavy electron liquid are best probed by NMR Knight shift measurements, which
provide a direct measure of the behavior of the heavy electron liquid that
emerges below the Kondo lattice coherence temperature as the lattice of local
moments hybridizes with the background conduction electrons. Because the
transfer of spectral weight between the localized and itinerant electronic
degrees of freedom is gradual, the Kondo liquid typically coexists with the
local moment component until the material orders at low temperatures. The
two-fluid formula captures this behavior in a broad range of materials in the
paramagnetic state. In order to investigate two-fluid behavior and the onset
and physical origin of different long range ordered ground states in heavy
electron materials, we have extended Knight shift measurements to
URuSi, CeIrIn and CeRhIn. In CeRhIn we find that the
antiferromagnetic order is preceded by a relocalization of the Kondo liquid,
providing independent evidence for a local moment origin of antiferromagnetism.
In URuSi the hidden order is shown to emerge directly from the Kondo
liquid and so is not associated with local moment physics. Our results imply
that the nature of the ground state is strongly coupled with the hybridization
in the Kondo lattice in agreement with phase diagram proposed by Yang and
Pines.Comment: 9 pages, 13 figure
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Topological surface states above the Fermi level in Hf2Te2 P
We report a detailed experimental study of the band structure of the recently discovered topological material Hf2Te2P. Using the combination of scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy with surface K doping, we probe the band structure of Hf2Te2P with energy and momentum resolution above the Fermi level. Our experiments show the presence of multiple surface states with a linear Dirac-like dispersion, consistent with the predictions from previously reported band-structure calculations. In particular, scanning tunneling spectroscopy measurements provide experimental evidence for the strong topological surface state predicted at 460meV, which stems from the band inversion between Hf-d and Te-p orbitals. This band inversion comprised of more localized d states could result in a better surface-to-bulk conductance ratio relative to more traditional topological insulators
Magnetic structure and Kondo lattice behavior in CeVGe: an NMR and neutron scattering study
We present nuclear magnetic resonance (NMR), neutron diffraction,
magnetization, and transport measurements on a single crystal and powder of
CeVGe. This material exhibits heavy fermion behavior at low temperature,
accompanied by antiferromagnetic (AFM) order below 5.8 K. We find that the
magnetic structure is incommensurate with AFM helical structure, characterized
by a magnetic modulated propagation vector of with in-plane
moments rotating around the -axis. The NMR Knight shift and spin-lattice
relaxation rate reveal a coherence temperature K, and the presence
of significant antiferromagnetic fluctuations reminiscent of the archetypical
heavy fermion compound CeRhIn. We further identify a metamagnetic
transition above T for magnetic fields perpendicular to . We
speculate that the magnetic structure in this field-induced phase consists of a
superposition with both ferromagnetic and antiferromagnetic components, which
is consistent with the NMR spectrum in this region of the phase diagram. Our
results thus indicate that CeVGe is a hexagonal structure analog to
tetragonal CeRhIn.Comment: 13 pages, 11 figure
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