Nanocavity-Mediated Purcell Enhancement of Er in TiO 2 Thin Films Grown via Atomic Layer Deposition
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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Results for “Rare-earth”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Effect of Fluoride Anions on Nd(III) Electrode Processes and Nd Metal Recovery in LiCl–KCl–NdCl 3
Here, this work investigated the impact of fluoride anions on Nd metal recovery in LiCl–KCl–NdCl 3 electrolytes by introducing LiF at a molar F/Nd ratio of 9 at 773 K. The voltammetric measurements confirmed that the fluoride ions facilitated single-step Nd(III)/Nd reduction by promoting the stability of the Nd(III) state compared to two-step reduction (Nd(III)/Nd(II) and Nd(II)/Nd) in all-chloride electrolytes. The stabilized Nd(III) state in the LiF-containing electrolyte effectively suppressed partial Nd(III)/Nd(II) reduction and the back-dissolution of Nd metal via comproportionation. By suppressing these reactions, high round-trip Coulombic efficiencies of 77–86% were achieved in the LiF-containing electrolyte during selective Nd deposition–removal cycles compared to 53–59% in all-chloride electrolytes. The Faradaic yield for Nd metal recovery was estimated at 38.6% in the LiF-containing electrolyte following long-term electrolysis, more than three times higher than 11.3% in all-chloride electrolytes. These results confirm the beneficial effect of fluoride ions on Nd metal recovery in low-melting chloride-based electrolytes, promising efficient Nd recovery at low temperatures.
11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Magnon-magnon coupling in an all-oxide insulator garnet Y 3 Fe 5 O 12 /Tm 3 Fe 5 O 12 heterostructure
Hybrid magnonic systems have recently attracted significant attention due to their intriguing physics and potential applications in coherent information processing. In this regard, we have investigated magnon-magnon coupling in the all-oxide insulator garnet Y 3 Fe 5 O 12 (YIG)/Tm 3 Fe 5 O 12 (TmIG) heterostructure. The presence of an avoided mode crossing region between the ferromagnetic resonance modes of YIG and TmIG indicates interfacial exchange coupling. This all-insulator system enables interfacial coupling via magnon-magnon interactions. The mode crossing occurs at 𝑓 𝑐 = 6.88 GHz, corresponding to the minimal resonance separation between the two hybrid modes. The coupling strength is determined to be 78 MHz (or 2.8 mT), providing clear evidence of magnon-magnon coupling between the two Kittel modes in the YIG/TmIG insulator system at 200 K. As a result, these findings pave the way for engineering magnonic band structures, tunable coherent magnonic interactions, and nonreciprocal spin transport, which are crucial for advancing ultralow-power magnonic devices.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Distinct effect of Kondo physics on crystal field splitting in electron and spin spectroscopies
Magnetic anisotropy is a key feature of rare earth materials from permanent magnets to heavy fermions. Here we explore the complex interplay of Kondo physics and anisotropy, and their effect on different experimental probes of magnetic anisotropy in a minimal 𝐽=3/2 Anderson impurity model using the numerical renormalization group. While anisotropy suppresses Kondo screening, virtual valence fluctuations enhance the anisotropy. We find distinct renormalization of the magnetic anisotropy measured via dynamical spin response (inelastic neutron scattering) versus electronic excitations in the impurity spectral function (resonant inelastic x-ray and scanning tunneling spectroscopy). The two measurement types have different responses and dependencies on the temperature and Kondo scales.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Collinear ferromagnetism with reduced moment length in kagome magnet Nd 3 Ru 4 Al 12
Here, we determine the magnetic ground state of the kagome lattice magnet Nd 3 Ru 4 Al 12 by single-crystal neutron diffraction, supported by experiments with polarized neutrons. We identify this material as a collinear ferromagnet (“hex-FM”) with uniform moment length and ordering vector 𝑸 = 0, in contrast to a previous, seminal report that proposed unequal moment lengths on two Nd sites, here called the “ortho-FM” state. Our analysis of the flipping ratio in polarized neutron scattering is consistent with the hex-FM state. The results provide a microscopic basis for understanding the large fluctuation-induced Hall and Nernst responses near 𝑇 C ≈ 41K, as previously reported for Nd 3 Ru 4 Al 12 .
RKKY interaction↗
Low-temperature magnetic structure and lattice response in SmCuAs 2
We investigated the structural and magnetic properties of single-crystalline SmCuAs 2 using high-resolution synchrotron x-ray diffraction and x-ray resonant magnetic scattering (XRMS) at the Sm 𝐿 2 and 𝐿 3 edges. Temperature-dependent diffraction measurements confirm that SmCuAs2 maintains its tetragonal symmetry from room temperature down to 8 K, with lattice parameters showing anomalous behavior below the resistivity minimum (𝑇≈30K). Notably, the c-axis lattice parameter exhibits a plateau and subsequent increase near the Néel temperature, indicating magnetoelastic coupling. XRMS measurements reveal a commensurate antiferromagnetic structure with a propagation vector 𝒒=(0,0,0.5). Our measurement shows that the Sm moments are aligned within the 𝒂𝒃 plane and arranged in a ++−− stacking along the 𝒄 axis. Comparison with related 𝑅𝐸CuAs 2 compounds (RE = Pr, Nd, and Gd) suggests that in-plane moment orientation and associated magnetic frustration play a key role in the emergence of the resistivity minimum. Differences in spin-orbit and magnetoelastic coupling across the series highlight their importance in governing low-temperature transport behavior.
36 MATERIALS SCIENCE↗
High-order harmonics and the reverse of the squaring up process in the triangular-lattice magnet HoPdAl 4 Ge 2
We uncover high-order harmonics and the reverse of the squaring-up process, in terms of analyzing the evolution of magnetic orders in a centrosymmetric layered triangular-lattice magnet HoPdAl 4 Ge 2 , based on a detailed study of the crystal structure, magnetic susceptibility, magnetization, heat capacity, and magnetic structure. Temperature dependencies of magnetic susceptibility and heat capacity show two magnetic transitions at T N = 10.5 K and T t = 5.5 K. Below T N , Ho 3+ spins order antiferromagnetically as a transverse spin-density wave with the propagation vector k 1 = (001.5 – δ) with δ ≈ 0.18. Upon further cooling through T t , the high-order harmonics with k n = (001.5 – nδ), n = 3, 5, 7 develop, suggesting a squaring-up process. It is surprising that the squaring-up process does not continue down to 0 K but reverses the trend below 3 K. Magnetic-field-induced metastable transitions were observed in M(H) curves with the fields applied both parallel and perpendicular to the triangular-lattice plane. Neutron-diffraction results suggest that the magnetization process in HoPdAl 4 Ge 2 involves the conversion of k n = (001.5 – nδ) with n = 1, 3, 5, 7, to a ferromagnetic k F = (000) component. It is worth noting that the already weak seventh harmonic magnetic peak is enhanced by applying a small magnetic field in the ab plane at 1.5 K or warming up to 3 K, accompanied by a slight decrease of δ.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Europium c -axis ferromagnetism in Eu ( Co 1 - x Ni x ) 2 - y As 2 : A single-crystal neutron diffraction study
Here we report neutron diffraction results for the body-centered-tetragonal series Eu(Co 1-x Ni x ) 2-y As 2 , x=0.10, 0.20, 0.42, and 0.82, y≤0.10, that detail changes to the magnetic ordering with nominal hole doping. We report the antiferromagnetic (AFM) propagation vectors, magnetic transition temperatures, and the ordered magnetic moments. We find a nonmonotonic change of the AFM propagation vector with x, with a minimum occurring at the tetragonal to collapsed-tetragonal phase crossover. For x=0.10 and 0.82 we find c-axis helix ordering of the Eu magnetic moments (spins) similar to x=0 and 1, with the spins oriented within the ab-plane. For x=0.20 and 0.42 we find higher-temperature c-axis ferromagnetic (FM) order and lower-temperature c-axis cone order. Using the extinction conditions for the space group, we discovered that the Eu spins are ordered in the higher-temperature c-axis FM phase for intermediate values of x, contrary to a previous report suggesting only Co/Ni spin ordering. Although we cannot directly confirm that the Co/Ni spins are also ordered, we suggest that c-axis itinerant-FM ordering of the Co/Ni spins could provide a molecular field that drives FM ordering of the Eu spins, which in turn provides the anisotropy for the lower-temperature c-axis cone order.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Disorder-induced local strain distribution in Y-substituted TmVO 4
We report an investigation of the effect of substitution of Y for Tm in Tm 1-x Y x VO 4 via low-temperature heat capacity measurements, with the yttrium content x varying from 0 to 0.997. Because the Tm ions support a local quadrupolar (nematic) moment, they act as reporters of the local strain state in the material, with the splitting of the ion's non-Kramers crystal field ground state proportional to the quadrature sum of the in-plane tetragonal symmetry-breaking transverse and longitudinal strains experienced by each ion individually. Analysis of the heat capacity, therefore, provides detailed insights into the distribution of local strains that arise as a consequence of the chemical substitution. These local strains suppress long-range quadrupole order for x > 0.22, and result in a broad Schottky-like feature for higher concentrations. Heat capacity data are compared to expectations for a distribution of uncorrelated (random) strains. For dilute Tm concentrations, the heat capacity cannot be accounted for by randomly distributed strains, demonstrating the presence of significant strain correlations between sites. For intermediate Tm concentrations, these correlations must still exist, but the data cannot be distinguished from that which would be obtained from a two-dimensional Gaussian distribution. The crossover between these limits is discussed in terms of the interplay of key lengthscales in the substituted material. Furthermore, the central result of this work, namely that local strains arising from chemical substitution are not uncorrelated, has implications for the range of validity of theoretical models based on random effective fields that are used to describe such chemically substituted materials, particularly when electronic nematic correlations are present.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Band Structure and Charge Ordering of Dirac Semimetal EuAl 4 at Low Temperatures
In this article, EuAl 4 is proposed to host a topological Hall state. This material also undergoes four consecutive antiferromagnetic (AFM) transitions upon cooling below T N1 = 15.4 K in the presence of charge density wave (CDW) order that sets in below T CDW = 140 K. We use angle-resolved photoemission spectroscopy and density-functional-theory calculations to study how magnetic ordering affects the electronic properties in EuAl 4 . Here, we found changes in the band structure upon each of the four consecutive AFM transitions including band splitting, renormalizations, and appearance of new bands forming additional Fermi sheets. In addition we also found significant enhancement of the quasiparticles’ lifetime due to suppression of spin flip scattering, similar to what was previously reported for ferromagnetic EuCd 2 As 2 . Surprisingly, we observe that most significant changes in electronic properties occur not at T N1 , but instead at the AFM3 to AFM4 transition, which coincides with the largest drop in resistivity.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
High-field magnetic phase diagrams of the 𝑅Mn 6 Sn 6 (𝑅=Gd–Tm) kagome metals
𝑅Mn 6 Sn 6 (𝑅=Y, Gd–Lu) kagome metals are promising materials hosting flat electronic bands and Dirac points that interact with magnetism. The coupling between the two magnetic 𝑅 and Mn sublattices can drive complex magnetic states with potential consequences for spin and charge transport and other topological properties. Here, in this work, we use a detailed magnetic Hamiltonian to calculate and predict the magnetic phase diagrams for 𝑅Mn 6 Sn 6 kagome metals within the mean-field approximation. These calculations reveal a variety of collinear, noncollinear, and noncoplanar phases that arise from competition between various interlayer magnetic exchange interactions and magnetic anisotropies of the 𝑅 and Mn ions. We enumerate these phases and their magnetic space groups for future analysis of their impact on topological and trivial bands near the Fermi surface.
kagome metal↗
Crystal field splittings and magnetic ground state of the square-lattice antiferromagnets YbBi 2 ClO 4 and YbBi 2 IO 4 with J eff = $\frac{1}{2}$
Here, we report on the crystal field level splitting and magnetic ground state of the J eff = $\frac{1}{2}$ square lattice antiferromagnets YbBi 2 ClO 4 and YbBi 2 IO 4 using powder inelastic neutron scattering (INS) and neutron diffraction measurements. Both compounds exhibit a well-isolated Γ 7 doublet ground state under a tetragonal crystal field environment, confirming a robust J eff = $\frac{1}{2}$ picture with slight XY-type anisotropic character in the g-tensor. Notably, the ground state wave functions closely resemble the Γ 7 doublet expected in the perfect cubic limit, consistent with the nearly cubic ligand configuration of eight O 2- ions surrounding Yb 3+ . Below T N = 0.21 K, YbBi 2 IO 4 exhibits a stripe long-range magnetic order characterized by an ordering wave vector q m = (1/2, 0, 0) or its symmetry-equivalent (0, 1/2, 0), with magnetic moments aligned along q m . The ordered moment is approximately 79% of the classical prediction, significantly larger than expected from the isotropic J 1 -J 2 model, suggesting the possible involvement of exchange anisotropy in explaining this observation. We show that symmetry-allowed XXZ and bond-dependent anisotropic exchange terms in a square lattice can play a critical role in stabilizing the stripe order and suppressing the moment reduction as observed. These findings establish YbBi 2 ClO 4 and YbBi 2 IO 4 as unique platforms for exploring rich J eff = $\frac{1}{2}$ magnetism from two less investigated perspectives: (i) on a square lattice and (ii) within a (nearly) cubic ligand environment.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Anomalous proximitized transport in metal/quantum magnet heterostructure Bi 2 Ir 2 O 7 /Yb 2 Ti 2 O 7
Fluctuations of quantum spins play a crucial role in the emergence of exotic magnetic phases and excitations. The lack of the charge degree of freedom in insulating quantum magnets, however, precludes such fluctuations from mediating electronic transport. Here, we show that the quantum fluctuations of a localized frustrated magnet induce strong proximitized charge transport of the conduction electrons in a synthetic heterostructure comprising an epitaxial Bi 2 Ir 2 O 7 ultrathin film on a single crystal of Yb 2 Ti 2 O 7 . The proximity effects are evidenced by the scaling behavior of the Bi 2 Ir 2 O 7 resistance in correspondence with the dynamic scaling of the dynamic spincorrelation function of Yb 2 Ti 2 O 7 , which is a result of quantum fluctuations near a multiphase quantum critical point. The proximitized transport in Bi 2 Ir 2 O 7 can be effectively tuned by a magnetic field through suppressing the quantum spin fluctuations (QSFs) as well as inducing transitions via magnetic anisotropy in Yb 2 Ti 2 O 7 . In this study, we establish a pathway for harnessing QSFs in magnetic insulators with electric transport, offering exciting prospects for potential applications in the realm of quantum spintronics.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Controlling 4 f antiferromagnetic dynamics via itinerant electronic susceptibility
Optical manipulation of magnetism holds promise for future ultrafast spintronics, especially with lanthanides and their huge, localized 4 f magnetic moments. These moments interact indirectly by spin polarizing the conduction electrons (the Ruderman-Kittel-Kasuya-Yosida exchange interaction), influenced by interatomic orbital overlap, and the conduction electron's susceptibility around the Fermi level. Here, we study this influence in a series of 4 f antiferromagnets, Gd T 2 Si 2 ( T = Co, Rh, Ir), using ultrafast resonant x-ray diffraction. We observe a twofold increase in the ultrafast intersublattice angular momentum transfer rate between the materials, originating from modifications in the conduction electron susceptibility, as confirmed by first-principles calculations. Published by the American Physical Society 2024
36 MATERIALS SCIENCE↗
Spin-Photon Entanglement of a Single Er 3 + Ion in the Telecom Band
Entanglement between photons and a quantum memory is a key component of quantum repeaters, which allow long-distance quantum entanglement distribution in the presence of fiber losses. Spin-photon entanglement has been implemented with a number of different atomic and solid-state qubits with long spin coherence times, but none directly emit photons into the 1.5 − μ m telecom band where losses in optical fibers are minimized. Here, we demonstrate spin-photon entanglement using a single rare earth ion in the solid-state Er 3 + coupled to a silicon nanophotonic cavity, which directly emits photons at 1532.6 nm. We infer an entanglement fidelity of 73(3)% after propagating through 15.6 km of optical fiber. This work opens the door to large-scale quantum networks based Er 3 + ions, leveraging scalable silicon device fabrication and spectral multiplexing. Published by the American Physical Society 2025
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Crystal fields, exchange and dipolar interactions, and noncollinear magnons of erbium oxide
Here, we simulate the properties of magnons in erbium oxide, a noncollinear antiferromagnet, from an effective single-ion Hamiltonian, including exchange and long-range dipolar interactions. We parametrize the crystal-field splitting of Er 2 O 3 using Steven's operators and obtain the effective symmetry-dependent exchange constants between different erbium ions quenched by the crystal field at different symmetry sites. We apply the Holstein-Primakoff transformation to the noncollinear spin system and employ paraunitary diagonalization for the effective spin Hamiltonian. The addition of the dipolar interaction to the exchange magnon dispersion changes the magnon bands drastically. The long-range nature of the dipolar interaction provides challenges to convergence, however, we find that the averaged and normalized difference in the magnon dispersion is less than an averaged factor of 10 −6 if the dipolar interaction is included out to the 40th nearest neighbor.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Erbium quantum memory platform with long optical coherence via back-end-of-line deposition on foundry-fabricated photonics
Realizing scalable quantum interconnects necessitates the integration of solid-state quantum memories with foundry photonics processes. While prior photonic integration efforts have relied upon specialized, laboratory-scale fabrication techniques, this work demonstrates the monolithic integration of a quantum memory platform with low-loss foundry photonic circuits via back-end-of-line deposition. We deposited thin films of titanium dioxide (TiO 2 ) doped with erbium (Er) onto silicon nitride nanophotonic waveguides and studied Er optical coherence at subkelvin temperatures with photon echo techniques. Furthermore, we suppressed optical dephasing through ex-situ oxygen annealing and optimized measurement conditions, which yielded an optical coherence time of 64 μs (a 5-kHz homogeneous linewidth) and slow spectral diffusion of 27 kHz over 4 ms, results that are comparable to state-of-the-art Er nanophotonic devices. Combined with second-long electron spin lifetimes and demonstrated electrical control of Er emission, our findings establish Er:TiO 2 on foundry photonics as a manufacturable platform for ensemble and single-ion quantum memories.
Electro-optic effects↗
SiC Substrate Composition Effect on TGO Scale Growth in EBC Systems During High‐Temperature Steam Exposure
A systematic investigation was conducted on the oxidation behavior of silicon-bond coats within environmental barrier coating (EBC) systems applied to Si-carbide (SiC) substrates, aiming to understand how different underlying SiC substrates influence the bond coat's thermally grown oxide (TGO) and its properties. The study examined (Y/Yb) 2 Si 2 O 7 /Si coatings on three cost-effective surrogate SiC substrates (chemical vapor deposition [CVD]-grown β-SiC, sintered α-SiC, and reaction-bonded [RB] SiC) for SiC fiber /SiC matrix ceramic matrix composites (CMCs). Discrepancies in TGO growth were observed, with noticeably higher growth rates reported for the coated CMC specimens than for the four monolithic SiC specimens. The CMC samples produce an amorphous TGO, whereas the other monolithic substrates formed a crystalline TGO, which lowered the oxygen permeability through the SiO 2 scale. In conclusion, the vitrification of the TGO in the (Y/Yb) 2 Si 2 O 7 /Si/CMC system resulted from the migration of boron species from the CMC substrate to the SiO 2 scale, leading to network modification via boron doping.
EBC↗