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The chemical bonding, structural and magnetic properties of EuPdSn2 have been investigated by DFT, synchrotron X-ray and neutron powder diffraction and 151Eu Mössbauer spectroscopy.

Amorphous films of tantalum oxide (Ta2O5) are widely applied to build highly reflective mirrors used in interferometric gravitational wave detectors, such as the Laser Interferometer Gravitational Wave Observatory (LIGO). Despite a large number of studies, the structural properties of amorphous Ta2O5 at the local scale still deserve several further investigations. Such information is essential to any attempt to understand the properties of this important material and no property modelling efforts can be expected to yield reliable information until the local structure in the amorphous phase is better understood. In this paper we report the results obtained by analysing the synchrotron X-ray pair distribution functions of pure and Ti-doped amorphous Ta2O5 film, deposited by ion beam sputtering, as prepared and after a thermal treatment. As a result, it is found that 1) the arrangement of Ta atoms in amorphous Ta2O5 strongly resembles that characterizing the high-pressure Z-Ta2O5 polymorph, whereas the topological properties of O atoms resembles that observed in delta-Ta2O5; 2) structural correlations in amorphous Ta2O5 start to vanish above ~ 5 Angstrom and are completely suppressed for r > 10 Angstrom on account of disorder; 3) Ti substitution retains the short-range topological ordering characterizing the as prepared Ta2O5 amorphous film even after thermal treatment; conversely, pure Ta2O5 films undergoes a significant rearrangement of the local structure after thermal treatment.

The new intermetallic compound Eu2Pd2Sn has been investigated. A single crystal was selected from the alloy and was analyzed by single-crystal X-ray diffraction, revealing that this compound possesses the noncentrosymmetric Ca2Pd2Ge structure type being, so far, the only rare-earth-based representative. Bonding analysis, performed on the basis of DOS and (I)COHP, reveals the presence of strong covalent Sn–Pd bonds in addition to linear and equidistant Pd–Pd chains. The incomplete ionization of Eu leads to its participation in weaker covalent interactions. The magnetic effective moment, extracted from the magnetic susceptibility χ(T) is μeff = 7.87 μB, close to the free ion Eu2+ value (μeff = 7.94 μB). The maximum of χ(T) at TN ∼ 13 K indicates an antiferromagnetic behavior below this temperature. A coincident sharp anomaly in the specific heat CP(T) emerges from a broad anomaly centered at around 10 K. From the reduced jump in the heat capacity at TN a scenario of a transition to an incommensurate antiferromagnetic phase below TN followed by a commensurate configuration below 10 K is suggested., A new intermetallic compound, Eu2Pd2Sn, is so far the only rare-earth representative of the Ca2Pd2Ge structure type. Synthesis and characterization of the structure, together with magnetic properties, are discussed.

Taking profit that the ternary indides Ce2+ePd2-eIn form two branches of solid solutions allowing to access to ferromagnetic (FM, e > 0) or anti-ferromagnetic (AFM, e

We report on crystal structure, magnetic and thermal physical properties of EuPd$_2$Sn$_4$ stannide. From the magnetic susceptibility measurements a divalent state of Eu rare earth element was determined together with an antiferromagnetic (AFM) order at 11 K. By applying magnetic field, the magnetic behavior variation reveals a complex magnetic structure. Above a critical field Bc a ferromagnetic (FM)-like character starts to prevail. AFM and FM regimes are separated by a metamagnetic region. Heat capacity measurements confirm this behavior.

Precise knowledge of the energy and lifetime of 229mTh isomeric state has notable importance as a basis for a nuclear clock. Such a clock would be capable to extend precision on the oscillator frequency by up to four orders of magnitude compared to the presently best atomic clocks. However, the technique proposed for the clock requires that the isomeric state energy is accessible with existing laser systems. Previous measurement placed this state at ∼8 eV (150 nm), in the Vacuum Ultra Violet (VUV) range of the electromagnetic spectrum. A precise direct measurement of the energy of this state is necessary to determine whether the nuclear clock can be made using existing laser technology. We are developing a cryogenic microcalorimeter to measure the energy and lifetime of the 229mTh isomeric state directly. The experiment will use a 233U source whose alpha-decay will populate the 229mTh isomeric state with 2% probability. The subsequent decay of 229mTh will be measured by a Transition Edge Sensor (TES) with 5 microseconds. The single-photon TES has sufficient resolving power combined with high efficiency in the whole energy band for this experiment. Here we present a prototype of TES based on a 200 nm thick iridium-gold (Ir/Au) film which was tested with a pulsed laser source and demonstrated ∼0.8 eV energy resolution and 5.8 ± 2.1 μs signal recovery time.

The new intermetallic compound Eu2Pd2Sn has been investigated. A single crystal was selected from the alloy and was analyzed by single-crystal X-ray diffraction, revealing that this compound possesses the noncentrosymmetric Ca2Pd2Ge structure type being, so far, the only rare-earth-based representative. Bonding analysis, performed on the basis of DOS and (I)COHP, reveals the presence of strong covalent Sn-Pd bonds in addition to linear and equidistant Pd-Pd chains. The incomplete ionization of Eu leads to its participation in weaker covalent interactions. The magnetic effective moment, extracted from the magnetic susceptibility χ(T) is μeff = 7.87 μB, close to the free ion Eu2+ value (μeff = 7.94 μB). The maximum of χ(T) at TN ∼ 13 K indicates an antiferromagnetic behavior below this temperature. A coincident sharp anomaly in the specific heat CP(T) emerges from a broad anomaly centered at around 10 K. From the reduced jump in the heat capacity at TN a scenario of a transition to an incommensurate antiferromagnetic phase below TN followed by a commensurate configuration below 10 K is suggested.

In the heavy-fermion system $Yb_2Pd_2In_{1-x}Sn_x$, the interplay of crystal-field splitting, Kondo effect, and Ruderman-Kittel-Kasuya-Yosida interactions leads to complex chemical-, pressure-, and magnetic-field phase diagrams, still to be explored in full detail. By using a series of techniques, we show that even modest changes of parameters other than temperature are sufficient to induce multiple quantum-critical transitions in this highly susceptible heavy-fermion family. In particular, we show that, above $\sim 10$ kbar, hydrostatic pressure not only induces an antiferromagnetic phase at low temperature, but it likely leads to a reorientation of the Yb magnetic moments and/or the competition among different antiferromagnetic configurations.

Hydrogen exposure of Tb2Pd2Mg crystallizing in the tetragonal Mo2FeB2 structure results in the absorption 8 ± 1 H/f.u. The absorption is not reversible and leads to a structure transition yielding a new structure type (Pearson symbol oI40, space group Fmmm). Tb2Pd2Mg is an antiferromagnet with TN ≈ 60 K showing 2 metamagnetic transitions. Upon hydrogenation the susceptibility cusp related to AF ordering disappears and the susceptibility increases monotonously with decreasing temperature. Magnetic remanence, which starts to develop below 20–25 K, can be attributed to a randomness in H sites occupancy.

Shastry-Sutherland lattice was observed as alternative ground state in Rare Earth intermetallic with Mo$_2$B$_2$Fe and U$_2$Pt$_2$Sn anisotropic structures where magnetic frustration is favored. In the case of Ce$_2$Pd$_2$Sn, it was shown that such phase can be suppressed by the application of magnetic field and, in this work, its stability is studied as a function of the electronic concentration by doping the Sn(4+) lattice with In(3+) atoms. Magnetic and specific heat measurements show that around 50\% substitution the Shastry Sutherland lattice vanishes in a critical point. This result confirms the strong dependence of that phase on the electron density because a recent investigation on the Pd rich solid solution Ce$_{2+\epsilon}$Pd$_{2-\epsilon}$In$_{1-x}$Sn$_x$ (with $\epsilon 0$ character stabilizes the ferromagnetic ground state all along the concentration, allowing the Shastry Sutherland lattice formation on the Sn rich side.

We report on synthesis, crystal structure, magnetic, thermodynamic, and transport properties of the compound ${\mathrm{YbPd}}_{2}\mathrm{In}$, crystallizing as a Heusler structure type. A trivalent state of the rare earth was determined by fitting the magnetic susceptibility with a Curie-Weiss law. This compound is characterized by showing very weak magnetic interactions and a negligible Kondo effect. A specific-heat jump was observed at $T\ensuremath{\approx}250\phantom{\rule{0.28em}{0ex}}\mathrm{mK}$, followed at higher temperature by a power-law decrease of ${C}_{P}(T)/T$. The resulting large electronic entropy increase at very low temperature is rapidly shifted to higher temperature by the application of magnetic field. This magnetocaloric effect places ${\mathrm{YbPd}}_{2}\mathrm{In}$ as a very good candidate for adiabatic demagnetization cooling processes.

The physical properties of the very-heavy-fermion compound ${\mathrm{YbCu}}_{4}\mathrm{Ni}$ were characterized through structural, magnetic, thermal, and transport studies along nearly four decades of temperature ranging between 50 mK and 300 K. At high temperature, the crystal electric field level splitting was determined with ${\mathrm{\ensuremath{\Delta}}}_{1}({\mathrm{\ensuremath{\Gamma}}}_{6})=85\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and ${\mathrm{\ensuremath{\Delta}}}_{2}({\mathrm{\ensuremath{\Gamma}}}_{8})\ensuremath{\approx}200\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, the latter being a quartet in this cubic symmetry. An effective magnetic moment ${\ensuremath{\mu}}_{\mathrm{eff}}\ensuremath{\approx}3{\ensuremath{\mu}}_{B}$ is evaluated for the ${\mathrm{\ensuremath{\Gamma}}}_{7}$ ground state, while at high temperature the value for a ${\mathrm{Yb}}^{3+}$ ion is observed. At low temperature this compound shows the typical behavior of a magnetically frustrated system undergoing a change of regime at a characteristic temperature ${T}^{*}\ensuremath{\approx}200\phantom{\rule{0.16em}{0ex}}\mathrm{mK}$ into of Fermi-liquid-type ``plateau'' of the specific heat: ${C}_{m}{/T|}_{T\ensuremath{\rightarrow}0}$ = const. The change in the temperature dependence of the specific heat coincides with a maximum and a discontinuity in respective inductive and dissipative components of the ac susceptibility. More details about the nature of this ground state are revealed by the specific heat behavior under applied magnetic field.

A pressure-induced anomalous valence crossover without structural phase transition is observed in archetypal cubic YbCu5 based heavy Fermion systems. The Yb valence is found to decrease with increasing pressure, indicating a pressure-induced crossover from a localized 4f13 state to the valence fluctuation regime, which is not expected for Yb systems with conventional c–f hybridization. This result further highlights the remarkable singularity of the valence behavior in compressed YbCu5-based compounds. The intermetallics Yb2Pd2Sn, which shows two quantum critical points (QCP) under pressure and has been proposed as a potential candidate for a reentrant Yb2+ state at high pressure, was also studied for comparison. In this compound, the Yb valence monotonically increases with pressure, disproving a scenario of a reentrant non-magnetic Yb2+ state at the second QCP.

Magnetic, transport, and thermal properties of CeCu2Mg are investigated to elucidate the lack of magnetic order in this heavy-fermion compound with a specific heat value, Cmag/T|T→0≈1.2 J/mol K2 and robust effective magnetic moments (μeff≈2.46μB). The lack of magnetic order is attributed to magnetic frustration favored by the hexagonal configuration of the Ce sublattice. In fact, the effect of magnetic field on Cmag/T and residual resistivity ρ0 does not correspond to that of a Fermi liquid (FL) because a broad anomaly appears at Tmax≈1.2 K in Cmag(T)/T, without changing its position up to μ0H=7.5 T. However, the flattening of Cmag/T|T→0 and its magnetic susceptibility χT→0, together with the T2 dependence of ρ(T), reveal a FL behavior for T≤2 K which is also supported by Wilson and Kadowaki-Woods ratios. The unusual coexistence of FL and frustration phenomena can be understood by placing paramagnetic CeCu2Mg in an intermediate section of a frustration-Kondo model. The entropy, Smag, reaches 0.87Rln6 at T≃100 K, with a tendency to approach the expected value Smag=Rln6 of the J=5/2 ground state of Ce3+. Fil: Michor, H.. Technische Universitat Wien; Austria Fil: Sereni, Julian Gustavo Renzo. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Bajas Temperaturas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Giovannini, M.. CNR-SPIN Corso Perrone, Genova; Italia. Università degli Studi di Genova; Italia Fil: Kampert, E.. Helmholtz-Zentrum Dresden-Rossendorf; Alemania Fil: Salamakha, L.. Technische Universitat Wien; Austria Fil: Hilscher, G.. Technische Universitat Wien; Austria Fil: Bauer, E.. Technische Universitat Wien; Austria

Phase equilibria in the Yb−Pd−Sn ternary system at 600 °C were established in the Pd ≤ 75 at.% concentration range employing X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe micro-analysis (EPMA). Besides the known intermetallic compounds, three new ternary intermetallics were revealed in the system, together with homogeneity ranges into the ternary field for some binary phases. Magnetic properties for the new compounds were investigated revealing stable Yb states Yb3+ for Yb3Pd4Sn13 and Yb2+ for Yb5Pd39Sn56, whereas for Yb13Pd40Sn31 an unstable valency of Yb is suggested.

International audience; Hydrogen interaction with intermetallic compound Nd2Ni2Mg crystallizing in the tetragonal Mo2FeB2 type of structure leads to the formation of hydride/deuteride containing 7.4-8 H(D)/f.u. Hydrogen absorption is accompanied by a monoclinic deformation of the unit cell with the crystal structure data refined from Synchrotron XRD (Sp. gr. P2(1)/c; a = 11.60733(5) angstrom; b = 7.66057(3) angstrom; c = 11.78743(5) angstrom, beta = 92.4126(4)degrees, V = 1047.194(8) angstrom(3)) and high resolution powder XRD data. The formed interstitial hydride disproportionates during heating forming NdH2. Nd2Ni2Mg is an antiferromagnet with the Neel temperature T-N approximate to 19 K. Presence of another magnetic phase transition at 14 K together with two metamagnetic transitions indicates a complicated magnetic phase diagram. The hydrogenation reduces T-N to 1.0 K. (C) 2017 Elsevier Ltd. All rights reserved.

Low temperature thermal and magnetic measurements performed on ferro-magneticl (FM) alloys of composition Ce-2.15(Pd1-xAgx)(1.95)In-0.9 are presented. Pd substitution by Ag depresses T-C(x) from 4.1 K down to 1.1 K for x = 0.5, which is related to the increase of band electrons, with a critical concentration extrapolated to x(cr) approximate to 0.6. The T-C(x) decrease is accompanied by a weakening of the magnetization of the FM phase. At high temperature (T > 30 K) the inverse magnetic susceptibility reveals the presence of robust magnetic moments (2.56 >= mu(eff) >= 2.4 mu(B)), whereas the low value of the Curie-Weiss temperature theta(P) approximate to -10 K excludes any relevant effect from Kondo screening. The specific heat jump at T-C(x) decreases accordingly, while an anomaly emerges at a fixed temperature T* approximate to 1 K. This unexpected anomaly does not show any associated sign of magnetism checked by AC-susceptibility measurements. Since the total magnetic entropy (evaluated around T = T-C(x = 0)) practically does not change with Ag concentration, the transference of degrees of freedom from the FM component to the non-magnetic T* anomaly is deduced. The origin of this anomaly is attributed to an arising magnetic frustration of the ground state and the consequent entropy bottleneck produced by the divergent increasing of density of excitations at low temperature. Fil: Sereni, Julian Gustavo Renzo. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Física de Metales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Giovannini, M.. Università di Genova; Italia Fil: Gomez Berisso, Mariano. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Física de Metales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Gastaldo, Marcelo Fabian. Università di Genova; Italia

The ground state magnetic behaviour of Ce2(Pd0.8Ag0.2)2In and Ce2(Pd0.5Ag0.5)2In, found in the ferromagnetic branch of Ce2Pd2In, has been investigated by neutron powder diffraction at low temperature. Ce2(Pd0.8Ag0.2)2In is characterized by a ferromagnetic structure with the Ce moments aligned along the c-axis and values of 0.96(2) mB. The compound retains the P4/mbm throughout the magnetic transition, although the magnetic ordering is accompanied by a significant decrease of the lattice strain along [00l], suggesting a magnetostructural contribution. The magnetic behaviour of Ce2(Pd0.5Ag0.5)2In is very different; this compound exhibits an extremely reduced magnetic scattering contribution in the diffraction pattern, that can be ascribed to a different kind of ferromagnetic ordering, with extremely reduced magnetic moments (~ 0.1 mB) aligned along [0l0]. These results point to a competition between different types of magnetic correlations induced by Ag-substitution, giving rise to a magnetically frustrated scenario in Ce2(Pd0.5Ag0.5)2In., to be published in Journal of Physics: Condensed Matter

The role of crystal chemistry in YbCu5−xAux crystallizing in the FCC AuBe5-type structure is highlighted through the study of the 0.7 ⩾ x ⩾ 0.4 region. Magnetic frustration, due to the magnetic Yb-ions forming a network of edge-sharing tetrahedra, seems to play an important role in the evolution of the ground state of the system. Significant differences are found among the YbCu5−xAux compounds compared to the cubic isotypic systems YbCu5−xAgx and YbCu5.

The phase relations of the GdCo13−x Six system have been studied by means of scanning microscopy, microprobe analysis and x-ray diffraction. Single-phase samples GdCo9±δSi4∓δ (structure type LaFe9Si4 with space group I 4/mcm) ar ef ormed in a narrow composition range |δ| 0.2, where GdCo9Si4 forms as af ully ordered ternary compound. The magnetic properties of GdCo9Si4 have been investigated by ac susceptibility, magnetization, specific heat and resistivity measurements. These experiments reveal ferrimagnetism below about 47 K, which is analysed in terms of a two-sublattice molecular field model with a local moment Gd subsystem coupling antiparallel to the itinerant ferromagnetic Co 3d sublattice. The 3d–3d exchange of the latter is the driving force for the onset of long range magnetic order. The validity of the twosublattice model is demonstrated by high field measurements, showing that the ferrimagnetic coupling starts to break up at a lower critical field µ0 Hl � 27 T. The magnetic ground state of GdCo9Si4 has been analysed on a microscopic basis via LSDA electronic structure calculations. (Some figures in this article are in colour only in the electronic version)

Samples prepared across the YbCu 5-x Au x solid solution system remain cubic AuBe 5 -type up to x = 1.8. As the Au concentration x is increased, the Au atoms first replace the Cu atoms on the 4c sites of the F43m space group until the sites are fully occupied, and then replace atoms on the 16e sites until the structure becomes unstable. The composition at x = 1 is at the crossover between two kinds of disordered sublattices and the ground state properties follow a non-monotonic behaviour through x = 1.

Phase equilibria in the Ce–Pd–In system at 750 °C were investigated in the whole concentration range not including the Pd-rich region, employing optical microscopy, microprobe analysis and X-ray diffraction. Besides the known intermetallic compounds (CePdIn, CePdIn2, CePd2In, Ce8Pd24In and the double-branched solid solutions Ce1.95Pd2+2xIn1−x and Ce2+xPd1.85In1−x), eight novel ternary compounds were revealed in the system. Furthermore, Pd/In solubilities were found in some of the novel ternary compounds and in the equiatomic compound. The complex phase equilibria resulting from the large number of binary and ternary compounds were determined.

Phase equilibria in Tb–Pd–In and Ho–Pd–In systems at 750 °C were investigated in the region near the composition of 50 at.% Pd employing optical microscopy (LOM), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The phase equilibria of the systems exhibit strong similarities, showing, in addition to R 2 Pd 2 In-based solid solutions, large substitutional R/In solid solutions starting from the PdIn binary compound. Selected alloys of other R–Pd–In (R=Pr, …, Er) systems were also investigated. A comparison was made between these systems and Ce–Pd–In.

The increase of Tc with x in Al 1 − x Mg x B 2 is controlled by the Fermi level tuning at a "shape resonance" (i.e., the 2D-3D cross-over, at x = 0.66, of the topology of the Fermi surface of σ holes in the superlattice of boron mono-layers intercalated by Al 1 − x Mg x ions) and by the tensile "micro-strain" in the boron sub-lattice (due to the lattice misfit between the boron and the intercalated layers). The softening of the E2g phonon frequency with increasing boron tensile micro-strain e in the range 3% < e < 6% shows the increasing electron-lattice interaction. The linear scaling, for 0.66 < x < 1, of Tc vs. the Fermi temperature TF of the σ holes shows a constant coupling strength with kFξ0 = 90 (where kF is the Fermi wave vector and ξ0 is the Pippard coherence length) that points toward a vibronic pairing mechanism.

The ternary compounds Yb2T2In (T=Cu, Pd and Au) have been synthesized. The indides Yb2Au2In and Yb2Pd2In crystallize in the Mo2FeB2 structure type, while Yb2Cu2In proved to be isotypic with the W2CoB2 structure. Magnetic, resistivity and specific heat measurements revealed no magnetic order for any of the compounds but, while in Yb2Cu2In and Yb2Au2In the valence of Yb was observed to be ν=2, Yb2Pd2In exhibits intermediate valence behavior.

Thermal conductivity of superconducting MgB2 was studied in both the superconducting and the normal state region. The latter is almost equally determined by the electronic and the lattice contribution to the total thermal conductivity. In the superconducting state, however, the lattice contribution is larger. The electronic thermal conductivity below Tc was derived from the experimental data considering the Bardeen-Rickayzen-Tewordt theory together with the model of Geilikman. The analysis shows that electron scattering on static imperfections dominates.

Neutron diffraction measurements as well as temperature, field and pressure dependent resistivity studies demonstrate the occurence of a dome-like magnetic phase in Yb 2 Pd 2 (In 1 -x Sn x ) (0,5≲x≲0.9) with antiferromagnetic ordering (k = (0, 0, 1/2)), whereas both Yb 2 Pd 2 In and Yb 2 Pd 2 Sn are nonmagnetic. The ordered moment and the ordering temperature of this phase is a result of a U-shape-like concentration dependence of the Kondo temperarature when proceeding from Yb 2 Pd 2 In to Yb 2 Pd 2 Sn.

The intermetallic compounds R2Pd2In of the light rare earths R = Pr, Nd were investigated by means of powder neutron diffraction in the temperature range from 1.6 K to 15 K. The chemical structure is of Mo2FeB2 type according to the space group P4/mbm. Antiferromagnetic rare-earth ordering of modulated type corresponding to k = [0,0,1/2] and [1/4,1/4,0] was established below the Neel temperatures TN = 5 K and 8 K for R = Pr and Nd, respectively, in contrast to k≈[0.22,0,0] and k = [0,0,0] of the antiferromagnetic and ferromagnetic, nonstoichiometric Ce2Pd2In systems.

In the framework of a systematic investigation of the ternary alloys formed by magnesium with two different metals of the rare earth family, data obtained in a study of the Yb–Pr–Mg system are presented. In the isothermal section at 450°C, phases have been identified which are based on the ternary extensions of the binary compounds PrMg, PrMg 3 , Pr 5 Mg 41 and YbMg 2 . The PrMg 12 compound on the contrary shows very small ternary solid solubility. Two ternary compounds have also been identified: τ 1 , (Yb x Pr 1- x )Mg 2 (0.15⩽ x ⩽0.48), cF24–MgCu 2 Laves type and τ 2 ,≈(Yb x Pr 1- x )Mg 4.5 (0.12⩽ x ⩽0.40), cF440–GdMg 5 type. The trends of the lattice parameters and the general features of the isothermal section are discussed and compared with those of other magnesium ternary alloys with rare earth elements. The behaviour of the different MeMg 2 Laves phases is particularly highlighted.

Magnetization measurements and the field dependence of 63Cu NMR relaxation rates are used to analyse the effect of an external magnetic field H at the QCP in CeCu5.9Au0.1. It is argued that the scaling argument in which H is included through an effective temperature T eff = [ T 2 + ( μ B H / k B ) 2 ] 1 / 2 holds only in weak field, while in strong fields the data are rather accounted for by direct scaling of the field dependence of magnetization.

In this report, we present and discuss new results for NQR and μSR experiments in CeCu6−xAux, for x = 0.3 ( T N ≈ 0.5 K ) and x = 0.8 ( T N ≈ 1.8 K ), carried out as part of our study of the spin dynamics, the magnetic ground-state and precursor effects on approaching TN. In these compounds the NQR relaxation rate for T ⪢ T K is consistent with a relaxation process driven by screened local Ce moments with a weak temperature and x dependence on cooling. The low temperature effective screening increases with decreasing x. The low-temperature zero-field μSR reveals an enhanced relaxation rate that does not appear to follow a critical law as expected on approaching the ordering temperature.

The effect of the Ni/Ge substitution on the ground state of CeNi5 is presented. The new ternary germanides CeNi5−x Ge x (x = 0.1, 0.2) were prepared by arc melting techniques and compared with CeNi5. Both CeNi4.9Ge0.1 and CeNi4.8Ge0.2 crystallize in the CaCu5 structure. The samples resulted to be single phase as confirmed by X-ray diffraction (XRD) and by electron probe microanalysis (EPMA). No phase transition was observed from measurements of susceptibility, magnetization, resistivity and heat capacity, although substitution of Ge/Ni seems to favor the suppression of spin fluctuations.

The structural and magnetic properties of a series of novel compounds in the ternary CeMgY system have been studied by X-ray diffraction. SQUID magnetometry and XAS spectroscopy. The crystal structures of the compounds Ce0.34Y0.67Mg2 and Ce0.49Y0.51Mg4.7 have been refined by the Rietveld technique. Magnetic data are consistent with a tripositive ground state 2F52 for the cerium atom. The XAS measurements confirm this result. Crystal field effects are apparent in the magnetic data at temperatures below about 50 K in the compounds with higher Ce concentration.

63 Cu NQR–NMR relaxation measurements in CeCu 5.9 Au 0.1 are used to achieve insights on the k -integrated, low-energy, generalized susceptibility χ( k ,ω,H,T→0) around the quantum critical point. The response function indicated by neutron scattering, namely of 2D character with anomalous exponent and with ( ω / T ) scaling, appears to justify the main experimental findings. A breakdown of that form of χ is found to occur below a field-dependent temperature T ∗ (H) , where a behavior characteristic of a gapped system sets in.

Phase equilibria in the ternary system YPrMg have been studied by X-ray powder diffraction analysis, optical and scanning electron microscopy, and electron probe microanalysis. The isothermal section at 500 °C has been determined in the range 50–100 at.% Mg. The phase equilibria are characterized by the formation of the following rather extended solid solutions: (Y x Pr 1− x )Mg (continuous solid solution of cP2-CsCl type) and Y x Pr 1− x Mg 3 (0 ⩽ x ⩽ 0.5) of cF16-BiF 3 type. A cubic phase of (Y x Pr 1− x )Mg 2 , (cF24-CuMg 2 type) derived from the binary PrMg 2 phase by a substitution of Pr with Y has been observed in a narrow range close to x ≈ 0.6. A solid solution based on the binary YMg 2 phase, i.e. ( Y x Pr 1− x )Mg 2 + y of hP12-MgZn 2 type (0.79 ⩽ x ⩽ 1, for y = 0), extends into the ternary field. The ternary compound Y x Pr 1 − x Mg 5 (0.3 ⩽ x ⩽ 0.9) of the cF440-GdMg 5 type has been established. Finally, the YPrMg section has been compared with the similar YLaMg section studied previously and with an isothermal section predicted on the basis of the systematic trends of the rare earth alloy properties.

Ternary Y-La-Mg alloys have been studied by X-ray diffraction, optical microscopy, scanning electron microscopy, and electron probe microanalysis. Phase equilibria have been established in the isothermal section at 500 °C in the 50 to 100 at. Pct Mg composition range. The sections (YxLa1-x) Mg (continuous solid solution), (YxLa1-xMg2 (cF24-Cu2Mg type for 0 ≤x ≤ 0.72 and hP12-MgZn2 type for 0.82 ≤x ≤ 1 solid solutions), and YxLa1-xMg3 (0 ≤x ≤ 0.47) have been especially studied. The ≈YxLa1-xMg5 (0.35 ≤x ≤ 0.77) ternary compound (cF440-GdMg5 type) has been found. A reinvestigation of selected regions of the binary La-Mg and Y-Mg systems proved necessary. The La5Mg41 phase, not previously reported, has been found by the annealing of samples at 600 °C. The YMg2 phase shows a wide homogeneity range up to 73 at. Pct Mg. The ternary section has been compared with a simulated one that was created by placing sections of binary systems of Mg with different rare earth elements side by side. The results are related to the pseudolanthanide concept.

We have examined the electronic structure of the heavy fermion ${\mathrm{Yb}}_{2}{\mathrm{Pd}}_{2}\mathrm{Sn}$ in comparison with the superconductor ${\mathrm{YbPd}}_{2}\mathrm{Sn}$ by means of high-resolution photoelectron spectroscopy (PES) and resonant x-ray emission spectroscopy (RXES). The PES data are interpreted in light of the density of states calculated within the local density approximation plus the dynamical mean-field theory. Our analysis of the RXES data shows that the valence of Yb in ${\mathrm{Yb}}_{2}{\mathrm{Pd}}_{2}\mathrm{Sn}$ is weakly fluctuating, indicating weak but finite $c--f$ hybridization, and decreases slightly with temperature. In contrast, the Yb valence in ${\mathrm{YbPd}}_{2}\mathrm{Sn}$ is nearly 3$+$ and does not show any temperature dependence, suggesting that the Yb $4f$ electrons are localized and the superconductivity is due to the Pd conduction electrons. The constant initial state spectra at the Yb $4d--4f$ resonance for ${\mathrm{Yb}}_{2}{\mathrm{Pd}}_{2}\mathrm{Sn}$ clearly show resonant behavior for ${\mathrm{Yb}}^{3+}$ and antiresonance for ${\mathrm{Yb}}^{2+}$, indicating that the ${\mathrm{Yb}}^{3+}$ and ${\mathrm{Yb}}^{2+}$ states are intimately correlated.

The TiNiSi-type structure, antiferromagnetic ordering and divalent state of europium in EuPdSn have been confirmed by neutron powder diffraction. The Néel temperature is 16.2(3) K. The magnetic diffraction peaks can be indexed with a propagation vector k = [0, 0.217, q(z)] (q(z) ≤ 0.02) at 13.2 K, and k = [0, 0.276, 0] at 3.6 K, indicating an incommensurate antiferromagnetic structure at both temperatures. At 13.2 K, the best refinement is obtained with a sinusoidally modulated magnetic structure and europium magnetic moments oriented in the (a,b) plane with an azimuthal angle ϕ of 66(4)°relative to the a-axis. By 3.6 K, the magnetic structure of EuPdSn has transformed to an (a,b) planar helimagnetic structure (a 'flat spiral').

Low temperature magnetic and thermal ( C m ) properties of the ferromagnetic (FM) alloys Ce 2.15 (Pd 1− x Rh x ) 1.95 In 0.9 were investigated in order to explore the possibility for tuning towards a quantum critical point (QCP) by doping Pd with Rh. As expected, the magnetic transition decreases from T = 4.1K at x = 0 with increasing Rh concentration. However, the phase boundary splits into two transitions, the upper being antiferromagnetic (AF) whereas the lower FM. The AF phase boundary extrapolates to T N = 0 for x cr ≈ 0.65 whereas the first order FM transition vanishes at x ≈ 0.3. The quantum critical character of the T N → 0 point is inferred from the divergent T dependence of the tail of C m /T observed in the x = 0.5 and 0.55 alloys, and the tendency to saturation of the maximum of C m ( T N )/ T currently observed in exemplary Ce compounds when T N → 0. Beyond the critical concentration the unit cell volume deviates from the Vegard´s law in coincidence with a strong increase of the Kondo temperature. Fil: Sereni, Julian Gustavo Renzo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Bajas Temperaturas; Argentina Fil: Giovannini, M.. Università di Genova; Italia Fil: Gomez Berisso, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Bajas Temperaturas; Argentina Fil: Saccone, A.. Università di Genova; Italia

The title compound is obtained from a stoichiometric melt of the elements and its crystal structure is determined by powder XRD.