Magnetization, crystal structure and anisotropic thermal expansion of single-crystal SrEr2O4

The magnetization, crystal structure, and thermal expansion of a nearly stoichiometric Sr$_{1.04(3)}$Er$_{2.09(6)}$O$_{4.00(1)}$ single crystal have been studied by PPMS measurements and in-house and high-resolution synchrotron X-ray powder diffraction. No evidence was detected for any structural phase transitions even up to 500 K. The average thermal expansions of lattice constants and unit-cell volume are consistent with the first-order Gr\"uneisen approximations taking into account only the phonon contributions for an insulator, displaying an anisotropic character along the crystallographic \emph{a}, \emph{b}, and \emph{c} axes. Our magnetization measurements indicate that obvious magnetic frustration appears below $\sim$15 K, and antiferromagnetic correlations may persist up to 300 K.Comment: 6 pages, 5 figure, 2 table

Incommensurate antiferromagnetic order in the manifoldly-frustrated SrTb2_2O4_4 with transition temperature up to 4.28 K

The N$\acute{\rm e}$el temperature of the new frustrated family of Sr\emph{RE}$_2$O$_4$ (\emph{RE} = rare earth) compounds is yet limited to $\sim$ 0.9 K, which more or less hampers a complete understanding of the relevant magnetic frustrations and spin interactions. Here we report on a new frustrated member to the family, SrTb$_2$O$_4$ with a record $T_{\rm N}$ = 4.28(2) K, and an experimental study of the magnetic interacting and frustrating mechanisms by polarized and unpolarized neutron scattering. The compound SrTb$_2$O$_4$ displays an incommensurate antiferromagnetic (AFM) order with a transverse wave vector \textbf{Q}$^{\rm 0.5 K}_{\rm AFM}$ = (0.5924(1), 0.0059(1), 0) albeit with partially-ordered moments, 1.92(6) $\mu_{\rm B}$ at 0.5 K, stemming from only one of the two inequivalent Tb sites mainly by virtue of their different octahedral distortions. The localized moments are confined to the \emph{bc} plane, 11.9(66)$^\circ$ away from the \emph{b} axis probably by single-ion anisotropy. We reveal that this AFM order is dominated mainly by dipole-dipole interactions and disclose that the octahedral distortion, nearest-neighbour (NN) ferromagnetic (FM) arrangement, different next NN FM and AFM configurations, and in-plane anisotropic spin correlations are vital to the magnetic structure and associated multiple frustrations. The discovery of the thus far highest AFM transition temperature renders SrTb$_2$O$_4$ a new friendly frustrated platform in the family for exploring the nature of magnetic interactions and frustrations.Comment: 19 pages, 8 Figures, 1 Tabl

Distinct itinerant spin-density waves and local-moment antiferromagnetism in an intermetallic ErPd2 Si2 single crystal

Identifying the nature of magnetism, itinerant or localized, remains a major challenge in condensed-matter science. Purely localized moments appear only in magnetic insulators, whereas itinerant moments more or less co-exist with localized moments in metallic compounds such as the doped-cuprate or the iron-based superconductors, hampering a thorough understanding of the role of magnetism in phenomena like superconductivity or magnetoresistance. Here we distinguish two antiferromagnetic modulations with respective propagation wave vectors at Q± = (H ± 0.557(1), 0, L ± 0.150(1)) and QC = (H ± 0.564(1), 0, L), where (H, L) are allowed Miller indices, in an ErPd2Si2 single crystal by neutron scattering and establish their respective temperature- and field-dependent phase diagrams. The modulations can co-exist but also compete depending on temperature or applied field strength. They couple differently with the underlying lattice albeit with associated moments in a common direction. The Q± modulation may be attributed to localized 4f moments while the QC correlates well with itinerant conduction bands, supported by our transport studies. Hence, ErPd2Si2 represents a new model compound that displays clearly-separated itinerant and localized moments, substantiating early theoretical predictions and providing a unique platform allowing the study of itinerant electron behavior in a localized antiferromagnetic matrix

Wasserstoff und Deuterium in Vanadium als wechselwirkende Gittergase

Pressure-composition isotherms at temperatures between 150 and 550 °C for solutions of hydrogen and deuterium in vanadium and the temperature dependence of the heat capacity in a series of V_D alloys habe been determined in the single phase regions ($\alpha$-phase) of the V_H(D) phase diagrams. The concentration dependences of the partial molar enthalpies $\Delta$H$_{H(D)}$ and entropies $\Delta \overline{H}_{H(D)}$ of hydrogen and deuterium have been derived from the solubility data. For both isotopes $\Delta \overline{H}_{H(D)}$ decreases with incresing H of D concentration x = [H(D)]/[V] at low x and increases a higher H or D content, having a munimum near x $\approx$ 0.4. The concentration dependence of $\Delta \overline{S}_{H(D)D}$ shows a large negative deviation from the ideal configurational entropy for random occupation of tetrahedral interstitial sites. The heat capacity of V-D$_{x}$ contains a substantial excess contribution, which remains when estimated electronic and vibrational contributions are substracted from the experimental data. The experimental results are analyzed by means of Monte Carlo simulations of a lattice gas with repulsive short range interactions between hydrogen (deuterium) atoms. The essential features of the experimental results are described by a lattice gas model which includes hard core interactions (blocking effect) and finite repulsive interactions outside the hard core

Wasserstoff und Deuterium in Vanadium als wechselwirkende Gittergase

Pressure-composition isotherms at temperatures between 150 and 550 °C for solutions of hydrogen and deuterium in vanadium and the temperature dependence of the heat capacity in a series of V_D alloys habe been determined in the single phase regions ($\alpha$-phase) of the V_H(D) phase diagrams. The concentration dependences of the partial molar enthalpies $\Delta$H$_{H(D)}$ and entropies $\Delta \overline{H}_{H(D)}$ of hydrogen and deuterium have been derived from the solubility data. For both isotopes $\Delta \overline{H}_{H(D)}$ decreases with incresing H of D concentration x = [H(D)]/[V] at low x and increases a higher H or D content, having a munimum near x $\approx$ 0.4. The concentration dependence of $\Delta \overline{S}_{H(D)D}$ shows a large negative deviation from the ideal configurational entropy for random occupation of tetrahedral interstitial sites. The heat capacity of V-D$_{x}$ contains a substantial excess contribution, which remains when estimated electronic and vibrational contributions are substracted from the experimental data. The experimental results are analyzed by means of Monte Carlo simulations of a lattice gas with repulsive short range interactions between hydrogen (deuterium) atoms. The essential features of the experimental results are described by a lattice gas model which includes hard core interactions (blocking effect) and finite repulsive interactions outside the hard core

Datenbank der Löslichkeiten der Wasserstoffisotope Protium (H), Deuterium (D) und Tritium (T) in den Metallen V, Nb, Ta, Pd und den Legierungen V1−xNbx,V1−xTax,Nb1−xMox,Pd1−xAGxV_{1-x}Nb_{x}, V_{1-x}Ta_{x}, Nb_{1-x}Mo_{x}, Pd_{1-x}AG_{x}

This JÜL-report is a documentation of solubility data of the hydrogen isotopes protium and/or deuterium and/or tritium in the metals V, Nb, Ta, Pd and alloys$V_{1-x}Nb_{x}, V_{1-x}Ta_{x}, Nb_{1-x}Mo_{x}, Pd_{1-x}Ag_{x}$. The solubility has been determined by measurements of the pressure drop or increase, the pressure itself, the sample temperature and by the knowledge of the effective temperature, the volume and the sample mass. The JÜL-report shows the hydrogen solubility graphically in the form of the usual isotherms, but the main purpose is the numerical presentation of the equilibrium pressures, sample temperatures and hydrogen concentrations (given as ratio of hydrogen - to metal atoms)