25 research outputs found
Traversing the pyrochlore stability diagram; microwave-assisted synthesis and discovery of mixed B-site LnInSbO family
The lanthanide pyrochlore oxides LnBO are one of the most
intensely studied classes of materials within condensed matter physics, firmly
centered as one of the pillars of frustrated magnetism. The extensive chemical
diversity of the pyrochlores, coupled with their innate geometric frustration,
enables realization of a wide array of exotic and complex magnetic ground
states. Thus, the discovery of new pyrochlore compositions has been a
persistent theme that continues to drive the field in exciting directions. The
recent focus on the mixed B-site pyrochlores offers a unique route towards
tuning both local coordination chemistry and sterics, while maintaining a
nominally pristine magnetic sublattice. Here, we present a broad overview of
the pyrochlore stability field, integrating recent synthetic efforts in mixed
B-site systems with the historically established LnBO families. In
parallel, we present the discovery and synthesis of the entire LnInSbO
family (Ln: La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) located near
the boundary of the pyrochlore stability field using a rapid, hybrid
mechanicochemical/microwave-assisted synthesis technique. Magnetic
characterization on the entire class of compounds draws striking parallels to
the stannate analogs, suggesting that these compounds may host a breadth of
exotic magnetic ground states
Miscibility amongst AVSb kagome superconductors: design of mixed A-site AVSb (A: K, Rb, Cs) alloys
In this work we explore the chemical-property phase diagram of the
AVSb family through A-site alloying. We demonstrate full miscibility of
the alkali-site, highlighting that the three parent compounds are the terminal
ends of a single solid-solution. Using both polycrystalline and single crystal
methods, we map the dependence of the two primary electronic instabilities: (1)
the onset of charge density wave (CDW) order () and (2) the onset
of superconductivity () with alkali-site composition. We show
continuous trends in both and , including a region
of enhanced CDW stability in KCsVSb alloys. Together, our
results open new routes for chemical perturbation and exploration of the
chemical-property relationships in the class of AVSb kagome
superconductors
Fermi surface mapping and the nature of charge density wave order in the kagome superconductor CsVSb
The recently discovered family of AVSb (A: K, Rb Cs) kagome metals
possess a unique combination of nontrivial band topology, superconducting
ground states, and signatures of electron correlations manifest via competing
charge density wave order. Little is understood regarding the nature of the
charge density wave (CDW) instability inherent to these compounds and the
potential correlation with the accompanying onset of a large anomalous Hall
response. To understand the impact of the CDW order on the electronic structure
in these systems, we present quantum oscillation measurements on single
crystals of CsVSb. Our data provides direct evidence that the CDW
invokes a substantial reconstruction of the Fermi surface pockets associated
with the vanadium orbitals and the kagome lattice framework. In conjunction
with density functional theory modeling, we are able to identify split
oscillation frequencies originating from reconstructed pockets built from
vanadium orbitals and Dirac-like bands. Complementary diffraction measurements
are further able to demonstrate that the CDW instability has a correlated
phasing between neighboring VSb planes. These results provide critical
insights into the underlying CDW instability in AVSb kagome metals and
support minimal models of CDW order arising from within the vanadium-based
kagome lattice.Comment: 12 pages, 9 figure
Revisiting spin ice physics in the ferromagnetic Ising pyrochlore PrSnO
Pyrochlore materials are characterized by their hallmark network of
corner-sharing rare-earth tetrahedra, which can produce a wide array of complex
magnetic ground states. Ferromagnetic Ising pyrochlores often obey the
"two-in-two-out" spin ice rules, which can lead to a highly-degenerate spin
structure. Large moment systems, such as HoTiO and
DyTiO, tend to host a classical spin ice state with low-temperature
spin freezing and emergent magnetic monopoles. Systems with smaller effective
moments, such as Pr-based pyrochlores, have been proposed as excellent
candidates for hosting a "quantum spin ice" characterized by entanglement and a
slew of exotic quasiparticle excitations. However, experimental evidence for a
quantum spin ice state has remained elusive. Here, we show that the
low-temperature magnetic properties of PrSnO satisfy several
important criteria for continued consideration as a quantum spin ice. We find
that PrSnO exhibits a partially spin-frozen ground state with a
large volume fraction of dynamic magnetism. Our comprehensive bulk
characterization and neutron scattering measurements enable us to map out the
magnetic field-temperature phase diagram, producing results consistent with
expectations for a ferromagnetic Ising pyrochlore. We identify key hallmarks of
spin ice physics, and show that the application of small magnetic fields
(0.75T) suppresses the spin ice state and induces a long-range
ordered magnetic structure. Together, our work clarifies the current state of
PrSnO and encourages future studies aimed at exploring the
potential for a quantum spin ice ground state in this system
YbVSb and EuVSb, vanadium-based kagome metals with Yb and Eu zig-zag chains
Here we present YbVSb and EuVSb, two new compounds exhibiting
slightly distorted vanadium-based kagome nets interleaved with zig-zag chains
of divalent Yb and Eu ions. Single crystal growth methods are
reported alongside magnetic, electronic, and thermodynamic measurements.
YbVSb is a nonmagnetic metal with no collective phase transitions
observed between 60mK and 300K. Conversely, EuVSb is a magnetic kagome
metal exhibiting easy-plane ferromagnetic-like order below =32K
with signatures of noncollinearity under low field. Our discovery of
YbVSb and EuVSb demonstrate another direction for the discovery
and development of vanadium-based kagome metals while incorporating the
chemical and magnetic degrees of freedom offered by a rare-earth sublattice
Spin-orbit excitons and electronic configuration of the insulator SrIrOF
Here we report on the low-energy excitations within the paramagnetic
spin-orbit insulator SrIrOF studied via resonant inelastic
X-ray scattering, \textit{ab initio} quantum chemical calculations, and
model-Hamiltonian simulations. This material is a unique Ir
analog of SrIrO that forms when F ions are intercalated within the
SrO layers spacing the square lattice IrO bilayers of SrIrO.
Due to the large distortions about the Ir ions, our computations
demonstrate that a large single-ion anisotropy yields an =1 (1,
0) ground state wave function. Weakly coupled, excitonic modes out
of the =0 ground state are observed and are well-described by a
phenomenological spin-orbit exciton model previously developed for and
transition metal ions. The implications of our results regarding the
interpretation of previous studies of hole-doped iridates close to
fillings are discussed.Comment: 6 pages, 3 figure