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The magnetic properties of newly prepared Tm2Ir2O7 were investigated by means of magnetization and specific heat measurements and compared to the properties of other heavy rare-earth pyrochlore iri...

Low-temperature magnetic properties of Er2Zr2O7 were studied by magnetization measurements on a newly prepared single crystal. Simultaneously, powder neutron diffraction was employed to investigate its microscopic properties down to 0.3 K. Our low-temperature data demonstrate the presence of a magnetic signal (short-range correlations) by (i) bifurcation of zero-field-cooled (ZFC) and field-cooled (FC) data, and (ii) diffuse magnetic scattering signal developing well in agreement with the temperature development of bulk properties. The presented data are discussed in the frame of a spin-glass ground state in Er2Zr2O7.

Magnetic properties of PrCuAl3 and NdCuAl3 single crystals, adopting the tetragonal BaNiSn3-structure-type, are reported. Our magnetization and specific heat measurements revealed no magnetic ordering in PrCuAl3, while NdCuAl3 orders antiferromagnetically below TN = 2.45 K. The paramagnetic regime was investigated for both analogues revealing (i) the a-axis as the easy direction of magnetization with (ii) a relatively high uniaxial anisotropy energy of 13.2 meV for PrCuAl3 compared to a smaller value of 4.7 meV for NdCuAl3. The measured data are well explained by rare-earth ground state multiplet splitting in crystal electric field. A powder neutron diffraction experiment confirmed PrCuAl3 to remain paramagnetic down to 1.5 K. On the other hand, NdCuAl3 orders antiferromagnetically below TN with an incommensurate magnetic structure described by two propagation vectors k1 = (1/3 - δ1, 0, 0) and k2 = (1/7 - δ2, 1/7 - δ2, 0), where δ1 = 0.035(1) and δ2 = 0.007(1). The magnetic moments (of both magnetic modulations) are arranged within the basal plane with a small z-component moment allowed by the symmetry. Our results are discussed with respect to other RCuAl3 compounds.

The effects on the rare-earth crystal-field-splitting schemes of incorporation of large spin-orbit coupling ($5d$) ions, such as ${\text{Ir}}^{\text{4}}+$, into the rare-earth pyrochlores are largely unknown. We report on the preparation, specific heat, magnetization, and inelastic neutron-scattering study of ${\text{Er}}_{\text{2}}{\text{Ir}}_{\text{2}}{\text{O}}_{\text{7}}$ pyrochlore. An anomaly in specific heat and bifurcation of zero-field cooled and field cooled magnetization indicates an ordering of the Ir sublattice below 140 K, in good agreement with other rare-earth pyrochlore iridates. The Er sublattice ordering below 2 K can be considered short range as well, following the development of specific-heat and magnetization data down to low temperatures. The inelastic neutron scattering allowed us to unambiguously determine the crystal-field (CF) eigenenergies and parameters of ${\text{Er}}_{\text{2}}{\text{Ir}}_{\text{2}}{\text{O}}_{\text{7}}$, which are dictated dominantly by nearest-neighbor anions (the oxygen cage around the Er cation). The influence of the magnetic iridium cations on the erbium CF scheme is rather moderate despite the strong spin-orbit coupling expected in a $5d$ metal, which is evident when comparing the energy spectra of this iridate and other $3d$- or $4d$-metal containing erbium pyrochlores. The determined CF parameters were subsequently utilized for calculations of magnetization and specific-heat CF contributions, leading to an excellent agreement with experimental data.

There is an ongoing dispute in the community about the absence of a magnetic quantum critical point (QCP) in the noncentrosymmetric heavy fermion compound CeRhSi

The magnetic properties of pyrochlore iridate Dy2Ir2O7 prepared by CsCl flux method were investigated by means of heat capacity and magnetization measurements. The low temperature behaviour was confirmed to be consistent with previously published results, whereas the high temperature data and their analysis are presented for the first time. The bifurcation of zero field-cooled and field-cooled magnetization curves coincides well with the onset of the anomaly in specific heat pointing to an ordering of the iridium sublattice. We confront the previously determined Dy3+ CF scheme with our high-temperature magnetization and specific heat data. The difference between calculations and experimental data, represented by 20 K specific heat anomaly, suggests the behaviour beyond the mean field approximation. The Dy2Ir2O7 differs from the rest of the heavy rare-earth pyrochlore iridates, where the mean field approximation constitutes an adequate description. The deeper understanding of the Dy2Ir2O7 magnetic behaviour requires, among others, also the phonon spectra studies.

The LuPd2Si2 compound is a member of a large group of compounds crystallizing in the ThCr2Si2 tetragonal type of structure. The negative thermal expansion of the lattice parameter c was determined by means of an x-ray diffraction experiment performed at different temperatures between 3 K and 300 K. Temperature of transition to a superconducting state was calculated and experimentally confirmed at 0.6 K. Comparison between results of theoretical calculations based on the local spin density approximation (LSDA) and the generalized gradient approximation methods (GGA) is given in the article.

The tetragonal CeCuxAl4-x solid solutions show unusual inelastic neutron spectra containing additional excitations that cannot be explained by a standard crystalline electric field model assuming a single Ce trivalent ion. This observation was ascribed to a strong magnetoelastic coupling which leads to a formation of the vibron quasibound state. In this work, we present analysis of the specific heat data of CeCuxAl4-x (x ranging from 0.75 to 1.1) compounds. We show that the magnetic contribution in the paramagnetic region cannot be fitted within the standard crystalline electric field model using a single set of energy levels, in agreement with neutron scattering results. To describe the specific heat data, we introduce a model which assumes at least two different local surroundings of the cerium ions in the sample. It can serve as complementary or alternative view on the unusual excitation spectrum of this system and allows us to describe behavior of Ce(Cu,Al)4 compounds without introducing a vibron model. The analysis is confronted with previous structural studies and results of neutron scattering experiments.

We present the preparation and characterization of an $\mathrm{E}{\mathrm{r}}_{2}\mathrm{Z}{\mathrm{r}}_{2}{\mathrm{O}}_{7}$ single crystal. The material was studied by means of x-ray and neutron diffraction, magnetization, AC susceptibility, and specific heat measurements. The defect-fluorite type of cubic structure, previously reported as the crystal structure of $\mathrm{E}{\mathrm{r}}_{2}\mathrm{Z}{\mathrm{r}}_{2}{\mathrm{O}}_{7}$, is consistent with our x-ray powder diffraction data. The measurements of physical properties were performed in magnetic field applied along principal crystallographic directions. A negligible directional dependence of physical properties is observed at temperatures down to 3 K, and only minor differences can be traced at lower temperatures. A low-temperature anomaly in magnetization and specific heat data and its evolution with applied magnetic field is followed. A frequency-dependent shift of freezing temperature was observed in AC susceptibility. Several origins of the observed anomaly are discussed, leaving a spin-glass state as the most probable explanation.

The EuRu2P2 single crystal was investigated by means of magnetic, transport and thermodynamic studies at ambient and hydrostatic pressures. A small magnetocrystalline anisotropy with crystallographic [100] direction as an easy magnetization direction was found by experimental measurements and confirmed by first-principles calculations. We connect a previously reported change in the compressibility observed at room temperature to a rapid change of ordering temperature under applied hydrostatic pressure.

CeCuAl3 crystallizing in the tetragonal BaNiSn3-type structure and CeCuxAl4–x solid solutions were investigated by means of elastic and inelastic neutron scattering. Powder neutron diffraction brought information on both temperature evolution of crystallographic parameters and magnetic order at low temperatures. No structural change was observed in the investigated temperature range from 1.5 to 300 K. Weak magnetic peaks outside nuclear Bragg positions observed in solid solutions with 0.90 ≤ x ≤ 1.10 were described by the propagation vector k = (0.40 + δx, 0.60 + δy, 0), where δx ≈ 0.02 and δy ≈ 0.01. The magnetic structure of CeCu0.75Al3.25 consists of two components: an anti-ferromagnetic one described by the same k and a ferromagnetic one with k0 = (0, 0, 0) and magnetic moments lying within the tetragonal basal plane. The evolution of magnetic excitations as a function of Cu–Al concentration in CeCuxAl4–x was studied by inelastic neutron scattering. The measured spectra of CeCuAl3 and the solution wit...

The present study is focused on the preparation of single crystalline LaPd 2 Al 2 by the Czochralski method. Differential scanning calorimetry (DSC) and energy dispersive X-ray spectroscopy (EDX) analyses reveal that LaPd 2 Al 2 is an incongruently melting phase which causes difficulties for the preparation of single crystalline LaPd 2 Al 2 by the Czochralski method. Therefore several non-stoichiometric polycrystalline samples were studied for its preparation. Finally the successful growth of LaPd 2 Al 2 without foreign phases has been achieved by using a non-stoichiometric precursor with atomic composition 22:39:39 (La:Pd:Al). X-ray powder diffraction, EDX analysis and DSC were used for the characterisation. A single crystalline sample was separated from the ingot prepared by the Czochralski method using the non-stoichiometric precursor. The presented procedure for the preparation of pure single phase LaPd 2 Al 2 could be modified for other incongruently melting phases.

Polycrystalline YbAu2Si2 has been prepared by arc melting and a non-standard anisotropic thermal expansion is observed at low temperatures. A non-magnetic Yb2+ valence state is derived from magnetization, magnetic-susceptibility, heat-capacity and electrical-conductivity measurements in the temperature range from 0.3 to 300 K and at external pressures up to 3.2 GPa. By both experimental and theoretical investigations, YbAu2Si2 is confirmed to be a system with a weak electron-electron correlations and a small electron-phonon interaction. Application of hydrostatic pressure does not reveal any change of state in the range of applied pressures.

A series of single crystal Ni2MnGa1-xInx samples, varying in compositions between x = 0 to 0.15, were grown by Bridgman method. Critical temperatures were obtained from the magnetisation and electrical resistivity measurements. A Curie temperature and the temperatures of pre-martensitic and martensitic transformation decrease with increasing indium content. The decrease rate is faster than the rate published previously on polycrystalline samples, since no martensitic transformation was observed in our samples with the indium content x > 0.05. The results of X-ray diffraction measurements of low temperature martensitic phase show significant decrease of monoclinic lattice parameter a and increase of monoclinic lattice parameter c and γ angle with respect to increasing indium content. Composition dependence was observed also for the modulation vector in martensitic and pre-martensitic phase, where its x and y coordinates gain values around 3/7 and 1/3 respectively.

The solid-state reaction, hydrothermal synthesis and CsCl flux methods were employed preparing Er2Ir2O7 pyrochlore iridate. A mixture of initial Er2O3 and IrO2 oxides was thermally treated, following the temperature evolution of individual phases by means of x-ray diffraction and energy dispersive x-ray spectroscopy. Reactions by hydrothermal synthesis, using various commonly used mineralising agents, showed negligible increase in the pyrochlore phase fraction. The solid-state reaction method allowed a preparation of Er2Ir2O7, however the reacted mixture contained a high percentage (60%) of initial unreacted Er2O3. Adding an excess of IrO2 to the initial content improved the composition of the reacted sample (50% of Er2Ir2O7 for initial Er2O3:IrO2 ratio 0.9:2.1). Nevertheless, a secondary Er–Ir–O phase with slightly larger crystallographic unit cell was also created as an additional product. An optimised flux synthesis, consisting of repeated heating and regrinding cycles at 800 °C and using CsCl as a flux, provided the best conditions for single phase pyrochlore preparation. A sample with 94% Er2Ir2O7 was further improved by repeated reaction with additional excess IrO2 oxide. A successful preparation route for (at least) the heavy-rare earth pyrochlore iridates is established.

We have investigated a single crystal of the tetragonal intermetallic compound NdPd 5 Al 2 by means of magnetization, specific heat and magnetoresistivity measurements. NdPd 5 Al 2 orders antiferromagnetically below 1.3 K and exhibits a distinct magnetocrystalline anisotropy with the c -axis as the easy axis of magnetization. Magnetic phase diagram constructed on the basis of heat capacity and magnetization measurements is characterized by two different low-temperature phases and first-order phase transition in the zero field.

In this work, we report results of specific heat and magnetization measurements on a single crystal of Nd 2 IrIn 8 . The compound orders antiferromagnetically below the Neel temperature of 12.5(2) K. Nd 2 IrIn 8 exhibits magnetic anisotropy with c as the easy axis. Two sharp metamagnetic transitions are present at 2 K. The measured data have been used to construct the low-temperature phase diagram for H || c . The measured susceptibilities and specific heat are compared to results based on first-principles calculations of the crystal-field parameters.

A new simplified synthesis of an Er 2 Ti 2 O 7 single crystal is presented. The single crystal was prepared by a floating zone technique from the unreacted stoichiometric mixture of starting oxides Er 2 O 3 and TiO 2 . No intermediate reactions of constituent oxides were conducted in contrast to previous studies. We demonstrate a good quality of prepared single crystal by both thorough (microscopic) chemical and structural characterization of the material and measurements of previously reported low-temperature properties: An Er 2 Ti 2 O 7 single crystal was characterized by means of x-ray, electron and neutron diffraction techniques, and magnetization and specific heat measurements. The low-temperature magnetization was investigated by indirect measurement employing pre-calibrated Hall probes. The obtained low-temperature data are well comparable with previous reports and document a high quality of the prepared single crystal. Presented single crystal synthesis from an unreacted precursor is prospectively applicable to other rare-earth RE 2 Ti 2 O 7 pyrochlores.

There is an ongoing dispute in the community about the absence of a magnetic quantum critical point (QCP) in the noncentrosymmetric heavy fermion compound CeRhSi3. In order to explore this question we prepared single crystals of CeRh(Si1-x Ge x )3 with x = 0.05 and 0.15 and determined the temperature-pressure (T-p) phase diagram by means of measurements of the electrical resistivity. The substitution of isoelectronic but large Ge enforces a lattice volume increase resulting in a weakening of the Kondo interaction. As a result, the x = 0.05 and x = 0.15 compound exhibit a transition into the antiferromagnetic (AFM) at higher temperatures being T N = 4.7 K and T N1 = 19.7 K, respectively. Application of pressure suppresses T N (T N1) monotonically and pressure induced superconductivity is observed in both Ge-substituted compounds above p ⩾ 2.16 GPa (x = 0.05) and p ⩾ 2.93 GPa (x = 0.15). Extrapolation of T N(p) → 0 of CeRh(Si0.95Ge0.05)3 yields a critical pressure of p c ≈ 3.4 GPa (in CeRh(Si0.85Ge0.15)3 p c ≈ 3.5 GPa) pointing to the presence of an AFM QCP located deep inside the superconducting state.