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Structural evolution of Nd2NiO4.23 with temperature, indicating several 1st order phase transitions with sub-mesoscopic oxygen ordering and instant ordering kinetics below 800 K.

Orthoferrites are a class of magnetic materials with a magnetic ordering temperature above 600 K, predominant G-type antiferromagnetic ordering of the Fe-spin system and, depending on the rare-earth ion, a spin reorientation of the Fe spin taking place at lower temperatures. DyFeO3 is of particular interest since the spin reorientation is classified as a Morin transition with the transition temperature depending strongly on the Dy-Fe interaction. Here, we report a detailed study of the magnetic and structural properties of microcrystalline DyFeO3 powder and bulk single crystal using neutron diffraction and magnetometry between 1.5 and 450 K. We find that, while the magnetic properties of the single crystal are largely as expected, the powder shows strongly modified magnetic properties, including a modified spin reorientation and a smaller Dy-Fe interaction energy of the order of 10 {\mu}eV. Subtle structural differences between powder and single crystal show that they belong to distinct magnetic space groups. In addition, the Dy ordering at 2 K in the powder is incommensurate, with a modulation vector of 0.0173(5) c*, corresponding to a periodicity of ~58 unit cells., Comment: contains supplementary material

The universal theory of critical phase transitions describes the critical behavior at second-order phase transitions in infinitely large systems. With the increased contemporary interest in nanoscale materials, we investigated CoO nanoparticles by means of neutron scattering and found how the theory of critical phenomena breaks down in the nanoscale regime. Using CoO as a model system, we have identified a size-dependent nanocritical temperature region close to the antiferromagnetic phase transition where the magnetic correlation length of the nanoparticles converges to a constant value, which is significantly smaller than that of the saturated state found at low temperatures. This is in clear contrast to the divergence around TN observed for bulk systems. Our finding of nanocriticality in the magnetic phase transition is of great importance for the understanding of phase transitions at the nanoscale.

Este artículo presenta un resumen de la experiencia que el Laboratorio de Ahorro para el Retiro (LAR) del Banco Interamericano de Desarrollo (BID) ha desarrollado en sus cuatro años de existencia para promover el ahorro previsional voluntario en países como Chile, Colombia, México y Perú.

Lanthanide permanent magnets are widely used in applications ranging from nanotechnology to industrial engineering. However, limited access to the rare earths and rising costs associated with their extraction are spurring interest in the development of lanthanide-free hard magnets. Zero- and one-dimensional magnetic materials are intriguing alternatives due to their low densities, structural and chemical versatility, and the typically mild, bottom-up nature of their synthesis. Here, we present two one-dimensional cobalt(II) systems Co(hfac)2 (R-NapNIT) (R-NapNIT=2-(2'-(R-)naphthyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, R=MeO or EtO) supported by air-stable nitronyl nitroxide radicals. These compounds are single-chain magnets and exhibit wide, square magnetic hysteresis below 14 K, with giant coercive fields up to 65 or 102 kOe measured using static or pulsed high magnetic fields, respectively. Magnetic, spectroscopic, and computational studies suggest that the record coercivities derive not from three-dimensional ordering but from the interaction of adjacent chains that compose alternating magnetic sublattices generated by crystallographic symmetry.

Der 3D‐Druck von geometrisch komplexen Nanostrukturen ist auf dem Weg zu ersten Anwendungen. Die Auswahl an geeigneten Materialien ermoglicht metallische, halbleitende, isolierende, supraleitende und exotische magnetische Eigenschaften. Das 3D‐FEBID‐Verfahren schreibt mit dem Elektronenstrahl eines Raster‐Elektronenmikroskops wie mit einem Nanostift. Das Material wird als Gasstrom von Precursor‐Molekulen uber eine Hohlnadel zugefuhrt. Der Elektronenstrahl ermoglicht die hochlokale Fragmentierung dieser Molekule, die meist metallische Zielatome enthalten. Die lokale Verweildauer des Strahls steuert den Strukturaufbau in der Vertikalen, wahrend seine seitliche Bewegung zu geneigten, freistehenden Strukturen fuhrt. Eine Herausforderung ist die definierte Strahlsteuerung, um ein CAD‐Modell moglichst prazise in ein reales 3D‐Nanoobjekt zu uberfuhren. Fur die Zukunft soll eine simulationsgestutzte Software zur Steuerung des Elektronenstrahls auch Laien die Anwendung erleichtern. 3D‐FEBID ist bereits heute ein zuverlassiges und in vielerlei Hinsicht einzigartiges Verfahren zur Direktabscheidung funktionaler Nanostrukturen.

The antiferromagnetic structure of Tb

The crystal structure and magnetic correlations in triangular antiferromagnet $\mathrm{Fe}\mathrm{Ga}{}_{2}\mathrm{S}{}_{4}$ are studied by x-ray diffraction, magnetic susceptibility, neutron diffraction, and neutron inelastic scattering. We report significant mixing at the cation sites and disentangle magnetic properties dominated by major and minor magnetic sites. The magnetic short-range correlations at $0.77\phantom{\rule{0.28em}{0ex}}{\AA{}}^{\ensuremath{-}1}$ correspond to the major sites and being static at base temperature they evolve into dynamic correlations around 30--50 K. The minor sites contribute to the magnetic peak at $0.6\phantom{\rule{0.28em}{0ex}}{\AA{}}^{\ensuremath{-}1}$, which vanishes at 5.5 K. Our analytical studies of triangular lattice models with bilinear and biquadratic terms provide the ratios between exchanges for the proposed ordering vectors. The modeling of the inelastic neutron spectrum within linear spin-wave theory results in the set of exchange couplings ${J}_{1}=1.7,\phantom{\rule{0.28em}{0ex}}{J}_{2}=0.9,\phantom{\rule{0.28em}{0ex}}{J}_{3}=0.8\phantom{\rule{0.28em}{0ex}}\mathrm{meV}$ for the bilinear Heisenberg Hamiltonian. However, not all features of the excitation spectrum are explained with this model.

We have investigated the magnetic ground state of a novel one-dimensional compound, NaCr 2 O 4 , in which Cr 2 O 4 double chains, i.e. zig-zag chains are aligned parallel to the b -axis, by means of both muon-spin rotation and relaxation ( μ + SR) and neutron diffraction (ND) measurements. The μ + SR results reveal the formation of static antiferromagnetic order below Neel temperature ( T N = 124 K ). The ND measurements also demonstrate the appearance of magnetic Bragg peaks with the propagation vector k → = ( 1, 0, 1 ) below T N . Combined analyses of the μ + SR and ND data clarify that the Cr moments in each zig-zag chain are aligned ferromagnetically along the c -axis, whereas antiferromagnetically along the a -axis between the adjacent zig-zag chains.

Este documento presenta los hallazgos, lecciones y retos del Laboratorio de Ahorro para el Retiro (Laboratorio) de diversas intervenciones piloto para impulsar el ahorro voluntario previsional de trabajadores independientes y de bajos ingresos en Chile, Colombia, México y Perú. Las intervenciones fueron implementadas durante cuatro años utilizando diversas herramientas basadas en la economía del comportamiento y apoyadas por las posibilidades ofrecidas por nuevas tecnologías. Las cuatro lecciones principales que se obtuvieron son: (1) Las soluciones vinculadas a una fuente de ingreso tienen un impacto destacado en la generación de ahorro voluntario, pero su escalamiento a la población de trabajadores de bajos ingresos tiene muchos desafíos; (2) Los recordatorios para ahorrar son fáciles de escalar y costo-efectivos, aunque no siempre funcionan y tienen un impacto limitado; (3) Facilitar el ahorro debe acompañarse de una mejor educación financiera y previsional; (4) Apostar por el ahorro voluntario para el retiro necesita un liderazgo institucional que permita superar las barreras regulatorias, tecnológicas y las fallas de mercado que dificultan la puesta en práctica de soluciones de ahorro escalables y efectivas. Finalmente, el documento ofrece una perspectiva sobre cómo avanzar hacia un pilar de ahorro voluntario para toda la población adulta generando un entorno regulatorio favorable, diseñando productos financieros inclusivos y asegurando que la tecnología alcance a más personas para ofrecer canales de ahorro sencillos y accesibles.

Hole doping in Nd${}_{2}$NiO${}_{4.00}$ can be either achieved by substituting the trivalent Nd atoms by bivalent alkaline earth metals or by oxygen doping, yielding Nd${}_{2}$NiO${}_{4+\delta}$. In this study, we investigated the interplay between oxygen and spin ordering for a low oxygen doping concentration i.e. Nd${}_{2}$NiO${}_{4.10}$. Although the extra oxygen doping level remains rather modest with only one out of 20 possible interstitial tetrahedral lattice sites occupied, we observed by single crystal neutron diffraction the presence of a complex 3D modulated structure related to oxygen ordering already at ambient, the modulation vectors being $\pm$2/13\textit{\textbf{a*}}$\pm$3/13\textit{\textbf{b*}}, $\pm$3/13\textit{\textbf{b*}}$\pm$2/13\textit{\textbf{b*}} and $\pm$1/5\textit{\textbf{a*}}$\pm$1/2\textit{\textbf{c*}} and satellite reflections up to fourth order. Temperature dependent neutron diffraction studies indicate the coexistence of oxygen and magnetic ordering below T${}_{N}$ $\simeq$ 48 K, the wave vector of the Ni sublattice being \textbf{\textit{k}}=(100). In addition, magnetic satellite reflections adapt exactly the same modulation vectors as found for the oxygen ordering, evidencing a unique coexistence of 3D modulated ordering for spin and oxygen ordering in Nd${}_{2}$NiO${}_{4.10}$. Temperature dependent measurements of magnetic intensities suggest two magnetic phase transitions below 48 K and 20 K, indicating two distinct onsets of magnetic ordering for the Ni and Nd sublattice, respectively.

ZusammenfassungIn der Schweiz wurden im Jahr 2017 rund 1,85 Mrd. CHF an Nonprofitorganisationen (NPO) gespendet. Der Spendenmarkt ist gesättigt und durch die wachsende Anzahl an Stiftungen und Vereinen wächst der Wettbewerb weiter. Die NPOs müssen innovativ bleiben und das Fundraising weiterentwickeln, um langfristig überleben zu können. Eine Möglichkeit sind Onlinespenden, um Kosten zu sparen und eine größere Reichweite gegenüber herkömmlichen Medien zu erzielen. Um das Potenzial von Onlinespenden zu nutzen, werden in dieser Studie Soziale-Norm-Nudges zur Erhöhung der Spendenbereitschaft und Konversion auf Webseiten von NPO untersucht. Eine User-Gruppe bekam einen Nudge eingeblendet, eine Kontrollgruppe nicht. Anhand von Messwebapplikationen wie Google Analytics und Hotjar wurde das unterschiedliche Verhalten der beiden Gruppen aufgezeichnet. Statistisch wurde kein Einfluss der Nudges auf die Spendenbereitschaft oder Konversion festgestellt. Jedoch zeigten Heatmaps, wie das Klickverhalten und die Mausbewegungen der Webseitenbesucher waren. Daraus lässt sich ableiten, dass es durchaus Potenzial für Weiterentwicklungen gibt.

The authors study a charge-orbital-spin correlation of high-pressure synthesized quasi-one-dimensional NaMn${}_{2}$O${}_{4}$ and Li${}_{0.92}$Mn${}_{2}$O${}_{4}$ using a low-temperature neutron powder diffraction.

In this work we report the temperature and doping-level evolution of the crystallographic and magnetic properties of the Sr-doped cobaltates ${\mathrm{Ca}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{BaCo}}_{4}{\mathrm{O}}_{7}$. The noncollinear ferrimagnetic phase known for the magnetoelectric parent compound is found to persist only for a small amount of Sr doping ($x=0.02$) and is accompanied by a strong unit cell distortion. In turn, further Sr doping blurs this distortion of lattice parameters and favors other magnetic arrangements. In particular, this work focuses on an intermediate temperature region $62\phantom{\rule{0.28em}{0ex}}\mathrm{K}lTl82\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ that shows a plateau in the magnetization. Using neutron powder diffraction at selected temperatures and compositions, we have solved the magnetic structure of this intermediate phase. By means of the superspace group theory and its implementation in the Rietveld refinement, we found that the phase belongs to the superspace group $Pna{2}_{1}{1}^{\ensuremath{'}}(1/2,1/2,g)qq0s$ with a basic orthorhombic structure and a modulation of the magnetic moments along the $c$ axis. The propagation vector is $\mathbf{k}=(\frac{1}{2},\frac{1}{2},g)$ with $g\ensuremath{\sim}0.02$ and possibly dependent on temperature. A modulated spin structure with distinct behaviors of the triangular and kagome cobalt sites is reported in ``114'' cobaltates.

We report on our evaluation of field-induced magnetic moments in the paramagnetic state of the $\text{spin-}\frac{1}{2}$ antiferromagnetic trimerized (${J}_{1}\ensuremath{-}{J}_{2}\ensuremath{-}{J}_{2}$) chain compound ${\mathrm{Cu}}_{3}{({\mathrm{P}}_{2}{\mathrm{O}}_{6}\mathrm{OD})}_{2}$ with ${J}_{1}=111\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and ${J}_{2}=30\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ [M. Hase et al., Phys. Rev. B 76, 064431 (2007)]. Magnetic reflections with integer indices, generated by field-induced magnetic moments, were observed at neutron-diffraction experiments performed in an applied magnetic field, and we evaluated the magnitudes of the moments to be ${M}_{1}=0.43(2)\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}/\mathrm{Cu}$ and ${M}_{2}=0.013(10)\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}/\mathrm{Cu}$ on the two crystallographic ${\mathrm{Cu}}^{2+}$ (Cu1 and Cu2) sites, respectively, at 6 T and 1.6 K. The resulting ratio ${M}_{2}/{M}_{1}=0.03(2)$ is in good agreement with the theoretical value for the ratio of the magnetization at the two sites. We thus conclude that for this well-understood spin system (which has the advantage of being amenable to detailed theoretical calculations) the extracted field-induced magnetic moments reproduce the correct information on the magnetization. Our result leads us to believe that we can precisely evaluate exchange interactions in paramagnets with multiple exchange interactions and multiple crystallographic magnetic-ion sites by using field-induced magnetic moments in combination with macroscopic physical quantities. This idea is expected to be applicable to a wide variety of quantum and frustrated magnets without long-range order.

Spin liquids are highly correlated yet disordered states formed by the entanglement of magnetic dipoles$^1$. Theories typically define such states using gauge fields and deconfined quasiparticle excitations that emerge from a simple rule governing the local ground state of a frustrated magnet. For example, the '2-in-2-out' ice rule for dipole moments on a tetrahedron can lead to a quantum spin ice in rare-earth pyrochlores - a state described by a lattice gauge theory of quantum electrodynamics$^{2-4}$. However, f-electron ions often carry multipole degrees of freedom of higher rank than dipoles, leading to intriguing behaviours and 'hidden' orders$^{5-6}$. Here we show that the correlated ground state of a Ce$^{3+}$-based pyrochlore, Ce$_2$Sn$_2$O$_7$, is a quantum liquid of magnetic octupoles. Our neutron scattering results are consistent with the formation of a fluid-like state of matter, but the intensity distribution is weighted to larger scattering vectors, which indicates that the correlated degrees of freedom have a more complex magnetization density than that typical of magnetic dipoles in a spin liquid. The temperature evolution of the bulk properties in the correlated regime below 1 Kelvin is well reproduced using a model of dipole-octupole doublets on a pyrochlore lattice$^{7-8}$. The nature and strength of the octupole-octupole couplings, together with the existence of a continuum of excitations attributed to spinons, provides further evidence for a quantum ice of octupoles governed by a '2-plus-2-minus' rule. Our work identifies Ce$_2$Sn$_2$O$_7$ as a unique example of a material where frustrated multipoles form a 'hidden' topological order, thus generalizing observations on quantum spin liquids to multipolar phases that can support novel types of emergent fields and excitations.

Magnetic topological phases of quantum matter are an emerging frontier in physics and material science. Along these lines, several kagome magnets have appeared as the most promising platforms. Here, we explore magnetic correlations in the kagome magnet Co3Sn2S2. Using muon spin-rotation, we present evidence for competing magnetic orders in the kagome lattice of this compound. Our results show that while the sample exhibits an out-of-plane ferromagnetic ground state, an in-plane antiferromagnetic state appears at temperatures above 90 K, eventually attaining a volume fraction of 80% around 170 K, before reaching a non-magnetic state. Strikingly, the reduction of the anomalous Hall conductivity (AHC) above 90 K linearly follows the disappearance of the volume fraction of the ferromagnetic state. We further show that the competition of these magnetic phases is tunable through applying either an external magnetic field or hydrostatic pressure. Our results taken together suggest the thermal and quantum tuning of Berry curvature induced AHC via external tuning of magnetic order., The kagome magnet Co3Sn2S2 has complex magnetic behaviour and a topological band structure that yields a large anomalous Hall effect. Guguchia et al. find phase separation between ferro- and anti-ferromagnetic orders and that the volume-wise competition controls the anomalous Hall conductivity

We investigate the magnetic structure and the electric properties of $\mathrm{YC}{\mathrm{r}}_{0.5}\mathrm{F}{\mathrm{e}}_{0.5}{\mathrm{O}}_{3}$, which was earlier reported to feature ferroelectricity from nonequivalent spins due to the cation disorder. We find a centrosymmetric magnetic order at all temperatures below ${T}_{N}$, which is incompatible with magnetically induced ferroelectricity. Our dielectric and pyroelectric studies also do not support intrinsic ferroelectricity in this system.

To study the relationship between the properties of low-dimensional spin systems with weakly coupled Cu-triangles and their crystal structure, single crystals of $Cs_3Cu_3Cl_8OH$ (1) and the new $Cs_3Cu_3Cl_{7.6}Br_{0.4}OH$ (2) were grown. Both compounds are isostructural and crystallize in a monoclinic structure with space group $P2_1/c$. The magnetic susceptibility of (1) shows a maximum at $2.23 K$ and of (2) at $2.70 K$, which are attributed to antiferromagnetic phase transitions. Furthermore, the magnetization along the $b$-axis at $1.9 K$ for both compounds shows a spin-flop transition into a new antiferromagnetic phase. This transition occurs at $0.61 T$ for (1) and at $2.0 T$ for (2). The antiferromagnetic order can be suppressed by a magnetic field $B_{C1}= 1.1 T$ for (1) and $B_{C2}= 1.2 T$ for (2). First single crystal neutron diffraction measured on (1) at different temperatures reveals the magnetic signal on the top of the nuclear reflection at (-1 0 0). Its magnetic ordering temperature was found to be at $T_{N1}= 2.12(3) K$., Comment: Accepted Paper

Quantum spin liquids are materials that feature quantum entangled spin correlations and avoid magnetic long-range order at T = 0 K. Particularly interesting are two-dimensional honeycomb spin lattices where a plethora of exotic quantum spin liquids have been predicted. Here, we experimentally study an effective S = 1/2 Heisenberg honeycomb lattice with competing nearest and next-nearest-neighbour interactions. We demonstrate that YbBr3 avoids order down to at least T = 100 mK and features a dynamic spin–spin correlation function with broad continuum scattering typical of quantum spin liquids near a quantum critical point. The continuum in the spin spectrum is consistent with plaquette type fluctuations predicted by theory. Our study is the experimental demonstration that strong quantum fluctuations can exist on the honeycomb lattice even in the absence of Kitaev-type interactions, and opens a new perspective on quantum spin liquids., npj Quantum Materials, 5 (1), ISSN:2397-4648

Two Cu2+ coordination polymers [CuCl(pyz)2](BF4) 1 and [CuBr(pyz)2](BF4) 2 (pyz = pyrazine) were synthesized in the family of quasi two-dimensional (2D) [Cu(pyz)2]2+ magnetic networks. The layer connectivity by mono-atomic halide ligands is novel and results in significantly shorter interlayer distances. Structures were determined by single crystal X-ray diffraction. The isostructural compounds crystallize in the tetragonal space group P4/nbm. [Cu(pyz)2]2+ layers are connected by halide ions along the c-axis and charge is compensated by BF4- ions located in the voids of the 3D coordination network. Temperature dependent X-ray diffraction of 1 revealed the rigidity of the [Cu(pyz)2]2+ layers which do not expand between 5 K and room temperature, whereas the expansion along the c-axis amounts to 2 %. The magnetic susceptibility of 1 and 2 shows a broad maximum around 8 K, indicating quasi 2D antiferromagnetic interactions within the [Cu(pyz)2]2+ layers. 2D Heisenberg model fits result in J|| = 9.4(1) K for 1 and 8.9(1) K for 2. The inter-layer coupling is much weaker with |J| = 0.31(6) K for 1 and 0.52(9) K for 2. The electron density, experimentally determined and calculated by density functional theory, confirm the location of the singly occupied orbital (the magnetic orbital) in the tetragonal plane. The analysis of the spin density reveals a mainly σ-type exchange through the pyrazine. Kinks in the magnetic susceptibility indicate the onset of long-range 3D magnetic order below 4 K. The magnetic structures were determined by neutron diffraction. Magnetic Bragg peaks occur below TN = 3.9(1) K for 1 and 3.8(1) K for 2. The magnetic unit cell is doubled along the c-axis (k = 0, 0, 0.5). The ordered magnetic moments are located in the tetragonal plane and amount to 0.76(8) μB/Cu2+ for 1 and 0.6(1) μB/Cu2+ for 2 at 1.5 K. The moments are coupled antiferromagnetically both in the a-b plane and along the c-axis. The anisotropy of the Cu2+ g-tensor was determined from powder and single crystal ESR spectra as gx = 2.060(1), gz = 2.275(1) for 1 and gx = 2.057(1), gz = 2.272(1) for 2 at room temperature.

The origin of the metal-to-insulator transition (MIT) in RNiO3 perovskites with R = trivalent 4 f ion has challenged the condensed matter research community for almost three decades. A drawback for progress in this direction has been the lack of studies combining physical properties and accurate structural data covering the full nickelate phase diagram. Here we focus on a small region close to the itinerant limit (R = Pr, 1.5 K < T < 300 K), where we investigate the gap opening and the simultaneous emergence of charge order in PrNiO3. We combine electrical resistivity, magnetization, and heat capacity measurements with high-resolution neutron and synchrotron x-ray powder diffraction data that, in contrast to previous studies, we analyze in terms of symmetry-adapted distortion modes. Such analysis allow us to identify the contribution of the different modes to the global distortion in a broad temperature range. Moreover, it shows that the structural changes at the MIT, traditionally described in terms of the evolution of the interatomic distances and angles, appear as abrupt increases of all nonzero mode amplitudes at TMIT = TN ∼ 130 K accompanied by the appearance of new modes below this temperature. A further interesting observation is the existence of a nearly perfect linear correlation between the amplitude of the breathing mode associated to the charge order and the staggered magnetization below the MIT. Our data also uncover a previously unnoticed anomaly at T ∗ ∼ 60 K (∼0.4 × TMIT), clearly visible in the electrical resistivity, lattice parameters and some mode amplitudes. Since phase coexistence is only observed in a small temperature region around TMIT (∼±10 K), these observations suggest the existence of a hidden symmetry in the insulating phase. We discuss some possible origins, among them the theoretically predicted existence of polar distortions induced by the noncentrosymmetric magnetic order [Perez-Mato et al., J. Phys.: Condens. Matter 28, 286001 (2016); Giovanetti et al., Phys. Rev. Lett. 103, 156401 (2009)].

The magnetic and structural properties of polycrystalline ${\mathrm{Co}}_{4\ensuremath{-}x}{\mathrm{Ni}}_{x}{\mathrm{Nb}}_{2}{\mathrm{O}}_{9}$ ($x=1,2$) have been investigated by neutron powder diffraction, magnetization and heat capacity measurements, and density functional theory (DFT) calculations. For $x=1$, the compound crystallizes in the trigonal $P\overline{3}c1$ space group. Below ${T}_{N}=31$ K it develops a weakly noncollinear antiferromagnetic structure with magnetic moments in the $ab$ plane. The compound with $x=2$ has crystal structure of the orthorhombic $Pbcn$ space group and shows a hard ferrimagnetic behavior below ${T}_{C}=47$ K. For this compound a weakly noncollinear ferrimagnetic structure with two possible configurations in the $ab$ plane was derived from neutron diffraction study. By calculating magnetic anisotropy energy via DFT, the ground-state magnetic configuration was determined for this compound. The heat capacity study in magnetic fields up to 140 kOe provides further information on the magnetic structure of the compounds.

We investigated the influence of oxygen over-stoichiometry on apical oxygen disorder and magnetic correlations in Nd2NiO4+d (d~0.11) in the temperature range of 2-300 K by means of synchrotron x-ray powder diffraction, neutron single crystal and powder diffraction studies, combined with macroscopic magnetic measurements. In the investigated temperature range, the compound crystalizes in a tetragonal commensurate structure with the P42/ncm space group with excess oxygen atoms occupy the 4b (3/4 1/4 1/4) interstitial sites, coordinated by four apical oxygen atoms. Large and anisotropic thermal displacement parameters are found for equatorial and apical oxygen atoms, which are strongly reduced on an absolute scale compared to the Nd2NiO4.23 phase. Maximum Entropy analysis of the neutron single crystal diffraction data uncovered anharmonic contributions to the displacement parameters of the apical oxygen atoms, toward the nearest vacant 4b interstitial site, related to the phonon assisted oxygen diffusion mechanism. Macroscopic magnetization measurements and neutron powder diffraction studies reveal long-range antiferromagnetic ordering of the Ni-sublattice at TN ~ 53 K with a weak ferromagnetic component along the c-axis, while the long-range magnetic ordering of the Nd-sublattice occurs below 10 K. Temperature dependent neutron diffraction patterns show the appearance of a commensurate magnetic order at TN with the propagation vector k = (100) and the emergence of an additional incommensurate phase below 30 K, while both phases coexist at 2 K. The commensurate magnetic structure is best described by the P42/nc`m` Shubnikov space group. Refined magnetic moments of the Ni and Nd-sites at 2 K are 1.144(76) muB and 1.632(52) muB respectively. A possible origin of the incommensurate phase is discussed and a tentative magnetic phase diagram is proposed.

We report neutron-scattering and ac magnetic susceptibility measurements of the two-dimensional spin-1/2 frustrated magnet $\mathrm{BaCdVO}{({\mathrm{PO}}_{4})}_{2}$. At temperatures well below ${T}_{\mathsf{N}}\ensuremath{\approx}1\phantom{\rule{4.pt}{0ex}}\text{K}$, we show that only 34% of the spin moment orders in an up-up-down-down stripe structure. Dominant magnetic diffuse scattering and comparison to published $\mathrm{muon}\ensuremath{-}\mathrm{spin}\ensuremath{-}\mathrm{rotation}$ measurements indicates that the remaining 66% is fluctuating. This demonstrates the presence of strong frustration, associated with competing ferromagnetic and antiferromagnetic interactions, and points to a subtle ordering mechanism driven by magnon interactions. On applying magnetic field, we find that at $T=0.1$ K the magnetic order vanishes at 3.8 T, whereas magnetic saturation is reached only above 4.5 T. We argue that the putative high-field phase is a realization of the long-sought bond-spin-nematic state.

This study reports an international experience using the transfemoral ACURATE neo transcatheter heart valve (Boston Scientific, Marlborough, Massachusetts) for the treatment of degenerated surgical aortic bioprostheses.Transcatheter valve-in-valve procedures have emerged as an alternative to redo surgery. Supra-annular prostheses might be particularly useful in this indication.This is an international multicenter analysis including 85 patients from 14 centers in Europe and Canada undergoing an ACURATE neo valve-in-valve procedure from March 2015 to February 2019.Internal diameter of the degenerated bioprosthesis was 20.3 ± 2.1 mm. Prosthesis size S was used in 70 (82%) procedures. The median depth of implantation was 3 mm and the upper crown of the ACURATE neo was positioned above the stent posts of the degenerated bioprosthesis in 54 (64%) and inside in 31 (36%). Mean transvalvular gradient before discharge was significantly lower if the upper crown was above the degenerated bioprosthesis (13.7 ± 5.9 mm Hg vs. 19.5 ± 10.0 mm Hg; p = 0.001). However, a high position of the ACURATE neo resulted in embolization in 1 patient, conversion to open-heart surgery in 1, and need for reintervention due to transcatheter heart valve failure within the first 18 months of follow-up in 4.This early experience shows that a high implantation of the ACURATE neo with the upper crown above the stent posts of the degenerated bioprosthesis resulted in lower mean transvalvular gradients but a higher rate of malpositioning and early valve degeneration.