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Antiferromagnetic intermetallic compound EuRhGe$_3$3 crystalizes in a non-centrosymmetric BaNiSn$_3$3-type ($I4\, {\rm mm}$I4mm) structure. We studied its pressure-dependent crystal structure by using synchrotron powder x-ray diffraction at room temperature. Our results show a smooth contraction of the unit cell volume by applying pressure while preserving $I4\, {\rm mm}$I4mm symmetry. No structural transition was observed up to 35 GPa. By the equation of state fitting analysis, the bulk modulus and its pressure derivative were determined to be 73 (1) GPa and 5.5 (2), respectively. Furthermore, similar to the isostructural EuCoGe$_3$3, an anisotropic compression of a and c lattice parameters was observed. Our experimental results show a good agreement with the pressure-dependent structural evolution expected from theoretical calculations below 13 GPa. Reflecting a strong deviation from integer Eu valence, the experimental volume data appear to be smaller than those of DFT calculated values at higher pressures. [ABSTRACT FROM AUTHOR]

GALAXIES is an in‐vacuum undulator hard X‐ray micro‐focused beamline dedicated to the study of the electronic structure of materials with high energy resolution using both photoelectron spectroscopy and inelastic X‐ray scattering and under both non‐resonant (NR‐IXS) and resonant (RIXS) conditions. Due to the penetrating power of hard X‐rays and the 'photon‐in/photon‐out' technique, the sample environment is not a limitation. Materials under extreme conditions, for example in diamond anvil cells or catalysis chambers, thus constitute a major research direction. Here, the design and performance of the inelastic X‐ray scattering end‐station that operates in the energy range from ∼4 keV up to 12 keV is reported, and its capabilities are highlighted using a selection of data taken from recently performed experiments. The ability to scan 'on the fly' the incident and scattered/emitted X‐ray energies, and the sample position enables fast data collection and high experimental throughput. A diamond X‐ray transmission phase retarder, which can be used to generate circularly polarized light, will also be discussed in the light of the recent RIXS–MCD approach. The GALAXIES beamline, an in‐vacuum undulator hard X‐ray micro‐focused beamline at Synchrotron SOLEIL dedicated to the study of the electronic structure of materials with high energy resolution using both photoelectron spectroscopy and inelastic X‐ray scattering and under both non‐resonant and resonant conditions, is described [ABSTRACT FROM AUTHOR]

We report here on the application of Resonant Inelastic X-ray Scattering (RIXS) in correlated electrons systems under pressure. Thanks to its bulk sensitivity and superior resolving power, RIXS appears as a powerful spectroscopic technique to unravel the local electronic and magnetic properties of materials at extreme conditions. The method is illustrated in vanadium-oxides- and Fe-based superconductors at high pressure. [ABSTRACT FROM PUBLISHER]

Using high-resolution, lifetime removed, x-ray absorption spectroscopy at the As K edge, we evidence the strong sensitivity of the As electronic structure upon electron doping with Co or pressure change in BaFe2As2, at room temperature. Our results unravel the prominent role played by As-4p orbitals in the electronic properties of the Fe pnictide superconductors. We propose a unique picture to describe the overall effect of both external parameter doping and pressure, resolving the apparent contradiction between angle-resolved photoemission spectroscopy, transport, and absorption results, with the As-p states as a key ingredient. [ABSTRACT FROM AUTHOR]

It is established that the multiferroics RMn2O5crystallize in the centrosymmetric Pbam space group and that the magnetically induced electric polarization appearing at low temperature is accompanied by a symmetry breaking. However, both our present x-ray study-performed on compounds with R = Pr, Nd. Gd, Tb, and Dy-and first-principles calculations unambiguously rule out this picture. Based on structural refinements, geometry optimization, and physical arguments, we demonstrate in this Letter that the actual space group is likely to be Pm. This turns out to be of crucial importance for RMn2O5 multiferroics since Pm is not centrosymmetric. Ferroelectricity is thus already present at room temperature, and its enhancement at low temperature is a spin-enhanced process. This result is also supported by direct observation of optical second harmonic generation. This fundamental result calls into question the actual theoretical approaches that describe the magnetoelectric coupling in this multiferroic family. [ABSTRACT FROM AUTHOR]

The GALAXIES beamline at the SOLEIL synchrotron is dedicated to inelastic X-ray scattering (IXS) and photoelectron spectroscopy (HAXPES) in the 2.3-12 keV hard X-ray range. These two techniques offer powerful complementary methods of characterization of materials with bulk sensitivity, chemical and orbital selectivity, resonant enhancement and high resolving power. After a description of the beamline components and endstations, the beamline capabilities are demonstrated through a selection of recent works both in the solid and gas phases and using either IXS or HAXPES approaches. Prospects for studies on liquids are discussed. [ABSTRACT FROM AUTHOR]

Pressure is the cleanest way to tune heavy fermion systems to a quantum phase transition in order to study the rich physics and competing phases, and the comparison between ytterbium and cerium systems is particularly fruitful. We briefly review the mechanisms in play and show some examples of expected and unexpected behaviour. We emphasise the importance of the valence changes under pressure and show how modern synchrotron techniques can accurately determine this, including at low temperature. [ABSTRACT FROM AUTHOR]

Multiferroic materials in which magnetism and ferroelectricity coexist are a time-honored subject of study, opening the route for the next generation of electronic devices. Understanding the pronounced interplay between these properties is a current challenge, especially for the realization of multiferroic devices. One of the largest reversible magnetoelectric couplings has been evidenced in TbMn2O5, the reference compound of the so-called RMn2O5 multiferroics. The origin of this strong coupling has been intensively studied from the static properties. Here we report an inelastic neutron scattering investigation of the dynamic properties in this famous compound. Our work sheds light on the electromagnon, a hybrid mode theoretically predicted in multiferroics, which couples magnetic excitations with polar lattice degrees of freedom. We were able to determine in TbMn2O5 the exchange constants of a model Heisenberg Hamiltonian and to identify the spin excitation that transforms in the electromagnon on passing from the ferroelectric and magnetically collinear phase to the low temperature incommensurate and weakly ferroelectric one. Our results point to the unusual feature of the dynamic magnetoelectric coupling in this series of multiferroics. [ABSTRACT FROM AUTHOR]

We report on a survey of Fe electronic properties in the temperature-pressure phase diagram of the Co-doped pnictides BaFe2As2 superconductors by hard x-ray absorption spectroscopy at the Fe K edge in the high-resolution, partial fluorescence yield mode. The absorption spectra are found remarkably stable through the temperature-induced phase transitions while pressure leads to slight energy shift of the main edge but not of the pre-edge. The latter effect is ascribed to the lattice compression and band widening effects under pressure as confirmed by multiple scattering simulations. Our results suggest that from the Fe electronic structure point of view, doping and pressure are equivalent ways to destabilize the magnetic phase to the advantage of superconductivity. [ABSTRACT FROM AUTHOR]

We provide a complete picture of the valence instabilities of Yb in the heavy-fermion compound YbCu2Si2 by resonant inelastic x-ray scattering measurements (RIXS) at the Yb L3 edge under high pressure (up to 22 GPa) and at low temperatures (down to 7 K) in the vicinity of the magnetic ordered state. The valence shows a significant increase with pressure without reaching the full trivalent state even at the highest pressure. Its pressure dependence is marked by a pronounced change of slope around 10 GPa, a value close to the magnetic critical pressure Pc≈ 8 GPa. Our results suggest that magnetic order in YbCu2Si2 appears for a valence value v < 3. Unlike CeCu2Si2, valence fluctuations do not sustain superconductivity, which is likely destroyed by ferromagnetism. [ABSTRACT FROM AUTHOR]

There exists increasing evidence that the phase diagram of the high-transition temperature (Tc) cuprate superconductors is controlled by a quantum critical point. According to one distinct theoretical proposal, on decreasing the hole-carrier concentration a transition occurs to an ordered state with two circulating orbital currents per CuO2 square. Below the 'pseudogap' temperature T*(T*>Tc), the theory predicts a discrete order parameter and two weakly-dispersive magnetic excitations in structurally simple compounds which should be measurable by neutron scattering. Indeed, novel magnetic order and one such excitation were recently observed. Here, we demonstrate for tetragonal HgBa2CuO4+? the existence of a second excitation with local character, consistent with the theory. The excitations mix with conventional antiferromagnetic fluctuations, which points towards a unifying picture of magnetism in the cuprates that will probably require a multi-band description. [ABSTRACT FROM AUTHOR]

Spin-polarized neutron diffraction experiments have revealed an unusual q = 0 magnetic order in the model high-temperature superconductor HgBa2CuO4+δ (Hg1201) below the pseudogap temperature T* [Y. Li et aL, Nature (London) 455, 372 (2008)]. Together with results for the structurally more complex compound YBa2Cu3O6+δ (YBCO) [B. Fauqué et al., Phys. Rev. Lett. 96, 197001 (2006); H.A. Mook et al., Phys. Rev. B 78, 020506 (2008)], this establishes the universal existence of a genuine novel magnetic phase in underdoped cuprates with high maximal Tc (above 90 K at optimal doping). Here we report a systematic study of an underdoped Hg 1201 sample (Tc = 75 K), the result of which is consistent with the previously established doping dependence of the magnetic signal. We present an assumption-free analysis of all the data available for Hg1201. Depending on how the hole concentration is estimated, comparison with the results for YBCO leads to different scenarios for the competition between the q = 0 magnetic order and the spin-density-wave order found in heavily underdoped YBCO. [ABSTRACT FROM AUTHOR]

We report a polarized neutron-scattering study of the orbital-like magnetic order in strongly underdoped YBa2Cu3O6.45 and YBa2(Cu0.98Zn0.02)3O6.6. Their hole-doping levels are located on both sides of the critical doping pMI of a metal-insulator transition inferred from transport measurements. Our study reveals a drop down of the orbital-like order slightly below pMI with a steep decrease of both the ordering temperature Tmag and the ordered moment. Above pMI, substitution of quantum impurities does not change Tmag, whereas it lowers significantly the bulk ordered moment. The modifications of the orbital-like magnetic order are interpreted in terms of a competition with electronic liquid crystal phases around pMI. This competition gives rise to a mixed magnetic state in YBa2Cu3O6.45 and a phase separation in YBa2(Cu0.98Zn0.02)3O6.6. [ABSTRACT FROM AUTHOR]

The pseudogap region of the phase diagram is an important unsolved puzzle in the field of high-transition-temperature (high-Tc) superconductivity, characterized by anomalous physical properties. There are open questions about the number of distinct phases and the possible presence of a quantum-critical point underneath the superconducting dome. The picture has remained unclear because there has not been conclusive evidence for a new type of order. Neutron scattering measurements for YBa2Cu3O6+δ (YBCO) resulted in contradictory claims of no and weak magnetic order, and the interpretation of muon spin relaxation measurements on YBCO and of circularly polarized photoemission experiments on Bi2Sr2CaCu2O8+δ(refs 12, 13) has been controversial. Here we use polarized neutron diffraction to demonstrate for the model superconductor HgBa2CuO4+δ (Hg1201) that the characteristic temperature T* marks the onset of an unusual magnetic order. Together with recent results for YBCO, this observation constitutes a demonstration of the universal existence of such a state. The findings appear to rule out theories that regard T* as a crossover temperature rather than a phase transition temperature. Instead, they are consistent with a variant of previously proposed charge-current-loop order that involves apical oxygen orbitals, and with the notion that many of the unusual properties arise from the presence of a quantum-critical point. [ABSTRACT FROM AUTHOR]

The pseudogap region of the phase diagram is an important unsolved puzzle in the field of high-transition-temperature (high-Tc) superconductivity, characterized by anomalous physical properties. There are open questions about the number of distinct phases and the possible presence of a quantum-critical point underneath the superconducting dome. The picture has remained unclear because there has not been conclusive evidence for a new type of order. Neutron scattering measurements for YBa2Cu3O6+δ (YBCO) resulted in contradictory claims of no and weak magnetic order, and the interpretation of muon spin relaxation measurements on YBCO and of circularly polarized photoemission experiments on Bi2Sr2CaCu2O8+δ(refs 12, 13) has been controversial. Here we use polarized neutron diffraction to demonstrate for the model superconductor HgBa2CuO4+δ (Hg1201) that the characteristic temperature T* marks the onset of an unusual magnetic order. Together with recent results for YBCO, this observation constitutes a demonstration of the universal existence of such a state. The findings appear to rule out theories that regard T* as a crossover temperature rather than a phase transition temperature. Instead, they are consistent with a variant of previously proposed charge-current-loop order that involves apical oxygen orbitals, and with the notion that many of the unusual properties arise from the presence of a quantum-critical point. [ABSTRACT FROM AUTHOR]

The elucidation of the pseudogap phenomenon of the high-transition-temperature (high-Tc) copper oxides-a set of anomalous physical properties below the characteristic temperature T* and above Tc-has been a major challenge in condensed matter physics for the past two decades. Following initial indications of broken time-reversal symmetry in photoemission experiments, recent polarized neutron diffraction work demonstrated the universal existence of an unusual magnetic order below T* (refs 3, 4). These findings have the profound implication that the pseudogap regime constitutes a genuine new phase of matter rather than a mere crossover phenomenon. They are furthermore consistent with a particular type of order involving circulating orbital currents, and with the notion that the phase diagram is controlled by a quantum critical point. Here we report inelastic neutron scattering results for HgBa2CuO4+δ that reveal a fundamental collective magnetic mode associated with the unusual order, and which further support this picture. The mode's intensity rises below the same temperature T* and its dispersion is weak, as expected for an Ising-like order parameter. Its energy of 52-56 meV renders it a new candidate for the hitherto unexplained ubiquitous electron-boson coupling features observed in spectroscopic studies. [ABSTRACT FROM AUTHOR]

The series of multiferroics RMn2O5 is extensively studied for its quasicollinear spin arrangement, which results in an electrical polarization according to the exchange-striction model. Variations of the interatomic distances modified by the external pressure can strongly influence the multiferroic properties. Understanding this influence is of great importance, especially for the future realization of multiferroic devices. As PrMn2O5 is paraelectric at ambient pressure, it is the most suitable candidate to search for pressure induced multiferroicity. In this paper, we report the emergence of a new pressure induced magnetic phase in PrMn2O5 determined by powder neutron diffraction under pressure. This new magnetic phase presenting at relatively low pressure becomes completely exclusive at 8 GPa. The determination of its magnetic structure has thus been possible for the first time. More importantly, the magnetic structure stabilized under pressure should induce a strong spontaneous electric polarization due to the nearly perfect collinearity of the Mn3+ and Mn4+ spins. [ABSTRACT FROM AUTHOR]

Recently, RMn2O5 (R=rare earth, Bi, Y) type multiferroics have drawn considerable attention, because of magnetically induced ferroelectricity along with an extremely large magnetoelectric coupling. Here, we present a detailed study on NdMn2O5 which is a crucial composition between the nonferroelectric PRMn2O5 and ferroelectric SmMn2O5. We report the results of heat capacity, magnetization, dielectric permittivity, and electric polarization measurements along with an accurate description of the structural and microscopic magnetic properties obtained from high resolution x-ray and neutron diffraction studies. We show that NdMn2O5 is ferroelectric, although the magnitude of polarization is much weaker than that of the other multiferroic members. The direction of the polarization is along the crystallographic b axis and its magnitude can be tuned with the application of a magnetic field. Moreover, unlike the other multiferroic members of this series, ferroelectricity in NdMn2O5 emerges in an incommensurate magnetic state. The present study also provides evidence in support of the influence of the rare-earth size on the magnetoelectric phase diagram. [ABSTRACT FROM AUTHOR]

Polarized elastic neutron scattering measurements have been performed in the bilayer copper oxide system Bi2Sr2CaCu208+j&dgr;, providing evidence for an intra-unit-cell magnetic order inside the pseudogap state. That shows time reversal symmetry breaking in that state as already reported in Bi2Sr2CaCu208+j&dgr; through dichroism in circularly polarized photoemission experiments. The magnetic order displays the same characteristic features as the one previously reported for monolayer HgBa2Cu04+&dgr; and bilayer YBa2Cu306+x, demonstrating that this genuine phase is ubiquitous of the pseudogap of high temperature copper oxide materials. [ABSTRACT FROM AUTHOR]

We report here an extensive high pressure small-angle X-ray scattering study on 3D supercrystals self-assembled from colloidal spherical gold crystalline nanoparticule (NPs). We used a large variety of NPs with different gold core diameter, from 2 to 10 nm, grafted with different ligands: alkane-thiols or oleylamine. The self assembly of these various NPs leads to supercrystals of different structures: face centered cubic (FCC), body centered cubic (BCC), as well as the C14 Frank and Kasper phase. Using a Diamond Anvil Cell to apply pressure on these wide range of samples, we provide a unique overview on the mechanical properties of gold NPs supercrystals. In particular, bulk modulii have been determined from low pressure regime and the different behavior between FCC and BCC structures has been interpreted as due to an easier restructuring of the ligand conformation in the FCC structure compared to the BCC structure. At higher pressure, a fingerprint of irreversible structural transition has been observed. We have ascribed this irreversibility to the sintering of nanoparticles and confirmed this interpretation by transmission electron microscopy.

We report on High Pressure Small Angle X-ray Scattering (HP-SAXS) measurements on 3D face-centered cubic (FCC) supracrystals (SCs) built from spherical gold nanoparticles (NPs). Dodecane-thiol ligands are grafted on the surface and ensure the stability of the gold NPs by forming a protective soft layer. Under a hydrostatic pressure of up to 12 GPa, the SC showed a high structural stability. The bulk elastic modulus of the SC was derived from the HP-SAXS measurements. The compression of the SC undergoes two stages: the first one related to the collapse of the voids between the NPs followed by the second one related to the compression of the soft matrix which gives a major contribution to the mechanical behavior. By comparing the bulk modulus of the SC to that of dodecane, the soft matrix appears to be less compressible than the crystalline dodecane. This effect is attributed to a less optimized chain packing under pressure compared to the free chains, as the chains are constrained by both grafting and confinement within the soft matrix. We conclude that these constraints on chain packing within the soft matrix enhance the stability of SCs under pressure., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

This paper presents a study of the lattice dynamics in BaFe 2 Se 3 . We combined first-principle calculations, infrared measurements and a thorough symmetry analysis. Our study confirms that Pnma cannot be the space group of BaFe 2 Se 3 , even at room temperature. The phonons assignment requires Pm to be the BaFe 2 Se 3 space group, not only in the magnetic phase, but also in the paramagnetic phase at room temperature. This is due to a strong coupling between a short-range spin-order along the ladders, and the lattice degrees of freedom associated with the Fe-Fe bond length. This coupling induces a change in the bond-length pattern from an alternated trapezoidal one (as in Pnma ) to an alternated small/large rectangular one. Out of the two patterns, only the latter is fully compatible with the observed block-type magnetic structure. Finally, we propose a complete symmetry analysis of the BaFe 2 Se 3 phase diagram in the 0-600 K range., (© 2022 IOP Publishing Ltd.)

The room-temperature structural properties of the RMn 2 O 5 multiferroics have been investigated under pressure, using powder X-ray scattering and density functional theory (DFT) calculations. It was possible to determine the lattice parameters and the main atomic positions as a function of pressure. Good agreement was observed between the X-ray and DFT results for most of the determined crystallographic data. From the DFT calculations, it was possible to infer the pressure evolution of the exchange interactions, and this analysis led to the conclusion that the onset of the q = (½, 0, ½) magnetic structure under pressure is related to the increase in the J 1 super-exchange terms (due to the reduction in the Mn-O distances) compared with the Mn-R exchange interactions. In addition, the 1D antiferromagnetic character of the compounds should be reinforced under pressure.

X-ray scattering measurements were utilized to probe the effects of pressure on a series of ionic liquids, N-alkyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr 1A -TFSI) (A = 3, 6, and 9), along with mixtures of ionic liquid and 30 mol. % lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. No evidence was found for crystallization of the pure ionic liquids or salt mixtures even at pressures up to 9.2 GPa. No phase separation or demixing was observed for the ionic liquid and salt mixtures. Shifts in the peak positions are indicative of compression of the ionic liquids and mixtures up to 2 GPa, after which samples reach a region of relative incompressibility, possibly indicative of a transition to a glassy state. With the application of pressure, the intensity of the prepeak was found to decrease significantly, indicating a reduction in cation alkyl chain aggregation. Additionally, incompressibility of the scattering peak associated with the distance between like-charges in the pure ionic liquids compared to that in mixtures with lithium salt suggests that the application of pressure could inhibit Li + coordination with TFSI - to form Li[TFSI 2 ] - complexes. This inhibition occurs through the suppression of TFSI - in the trans conformer, in favor of the smaller cis conformer, at high pressures.

In solid state science, multifunctional materials and especially multiferroics have attracted a great deal of attention, as they open the possibility for next generation spintronic and data storage devices. Interestingly, while many of them host coexisting 3d and 4f elements, the role of the coupling between these two magnetic entities has remained elusive. By means of single crystal neutron diffraction and inelastic neutron scattering experiments we shed light on this issue in the particular case of the multiferroic oxide DyMn 2 O 5 . This compound undergoes a first order magnetic transition from a high temperature incommensurate phase to a low temperature commensurate one. Our investigation reveals that although these two phases have very different magnetic structures, the spin excitations are quite similar indicating a fragile low temperature ground state with respect to the high temperature one. Such a rare scenario is argued to be a manifestation of the competition between the exchange interaction and 4f magnetic anisotropy present in the system. It is concluded that the magnetic structure, hence the ferroelectricity, can be finely tuned depending on the anisotropy of the rare earth.

Using high-resolution, lifetime removed, x-ray absorption spectroscopy at the As K edge, we evidence the strong sensitivity of the As electronic structure upon electron doping with Co or pressure change in BaFe2As2, at room temperature. Our results unravel the prominent role played by As-4p orbitals in the electronic properties of the Fe pnictide superconductors. We propose a unique picture to describe the overall effect of both external parameter doping and pressure, resolving the apparent contradiction between angle-resolved photoemission spectroscopy, transport, and absorption results, with the As-p states as a key ingredient.

It is established that the multiferroics RMn(2)O(5) crystallize in the centrosymmetric Pbam space group and that the magnetically induced electric polarization appearing at low temperature is accompanied by a symmetry breaking. However, both our present x-ray study-performed on compounds with R=Pr,Nd,Gd,Tb, and Dy-and first-principles calculations unambiguously rule out this picture. Based on structural refinements, geometry optimization, and physical arguments, we demonstrate in this Letter that the actual space group is likely to be Pm. This turns out to be of crucial importance for RMn(2)O(5) multiferroics since Pm is not centrosymmetric. Ferroelectricity is thus already present at room temperature, and its enhancement at low temperature is a spin-enhanced process. This result is also supported by direct observation of optical second harmonic generation. This fundamental result calls into question the actual theoretical approaches that describe the magnetoelectric coupling in this multiferroic family.

In high-temperature copper oxide superconductors, a novel magnetic order associated with the pseudogap phase has been identified in two different cuprate families over a wide region of temperature and doping. We report here the observation below 120 K of a similar magnetic ordering in the archetypal cuprate La(2-x)Sr(x)CuO4 (LSCO) system for x=0.085. In contrast with the previous reports, the magnetic ordering in LSCO is only short range with an in-plane correlation length of ∼10  A and is bidimensional (2D). Such a less pronounced order suggests an interaction with other electronic instabilities. In particular, LSCO also exhibits a strong tendency towards stripes ordering at the expense of the superconducting state.