Samarium Magnetism Studied on SmPd2Al3 Single Crystal

In this paper, specific features of Sm magnetism in an intermetallic compound have been studied. For this purpose, a high-quality single crystal of SmPd2Al3 was grown and subjected to detailed measurements of specific heat, magnetization, ac susceptibility, and electrical resistivity with respect to temperature and a magnetic field applied along the principal crystallographic directions. SmPd2Al3 magnetism was found to be strongly anisotropic with the easy-magnetization direction along the c axis where the main magnetic features are concentrated. The a-axis response remains weak, paramagneticlike, even in the magnetically ordered state. Ferromagnetism with TC=12.4 K has been indicated by all the measured physical properties. At lower temperatures, three successive order-order phase transitions have been observed on the temperature dependence of the specific heat as three anomalies: at 3.4, 3.9, and 4.4 K, respectively. The low-temperature magnetization data can be understood within a scenario that considers the antiferromagnetic ground state as being gradually destroyed through a series of four metamagnetic transitions at 0.03, 0.35, 0.5, and 0.75 T, as detected in the 1.8 K magnetization data. The experimental data are discussed together with the results of electronic-structure and crystal-field calculations from first principles, which were performed as an important part of the study for comprehension and explanation of the observed behavior of the SmPd2Al3 compound

Heat Transfer Analysis of a Diesel Engine Head

This paper documents the research carried out at the Josef Božek Research Center of Engine and Automotive Engineering dealing with extended numerical stress/deformation analyses of engines parts loaded by heat and mechanical forces. It contains a detailed description of a C/28 series diesel engine head FE model and a discussion of heat transfer analysis tunning and results. The head model consisting of several parts allows a description of contact interaction in both thermal and mechanical analysis

Structural Stress Analysis of an Engine Cylinder Head

This paper deals with a structural stress analysis of the cylinder head assembly of the C/28 series engine. A detailed FE model was created for this purpose. The FE model consists of the main parts of the cylinder head assembly, and it includes a description of the thermal and mechanical loads and the contact interaction between their parts. The model considers the temperature dependency of the heat transfer coefficient on wall temperature in cooling passages. The paper presents a comparison of computed and measured temperature. The analysis was carried out using the FE program ABAQUS.

Neutron scattering study of the Tm2 Ir2 O7 pyrochlore iridate

The newly synthesized Tm2 Ir2 O7 iridate is investigated using neutron scattering techniques. Powder neutron diffraction patterns confirm that Tm2 Ir2 O7 crystallizes in a cubic structure of pyrochlore type, consistent with the rest of the rare-earth A2 Ir2 O7 series, and the crystal structure is preserved down to 0.2 K. The thermal expansion of the crystal lattice is well described by a Debye model of lattice vibrations. A weak magnetic signal consistent with the so-called all-in-all-out magnetic order (AIAO) is traced at low temperature; however, it cannot serve as unambiguous evidence of the AIAO structure in the compound. Nondispersive magnetic excitations in energy-momentum space are observed in inelastic neutron scattering spectra of Tm2 Ir2 O7. The crystal-field scheme and parameters of the thulium iridate are refined and discussed with respect to the specific heat and magnetization data. The results are supported by mean-field calculations

Basic nutritional properties of cornelian cherry (Cornus mas L.) cultivars grown in the Czech Republic

The ascorbic acid, total polyphenols, total anthocyanins and mineral content, together with antioxidant activity, was determined in five Czech, two Ukrainian and two Austrian cultivars of cornelian cherry (Cornus mas L.) widely grown in the Czech Republic. Ascorbic acid content varied between 199–433 mg kg−1, total polyphenols between 2174–6143 mg kg−1, and total anthocyanins between 61–253 mg kg−1. All fruits were good sources of major metals (K, Ca, Mg, Fe, and Mn) and trace elements (Cu, Zn, and Cr). The antioxidant activity was determined by EPR and DPPH radical scavenging assay and ranged from 29.5% to 67.2%. There was a linear relationship between antioxidant activity and total polyphenol content. Based on the obtained results, Ekotišnovský, Fruchtal, and Ruzyňský cultivars were recommended for further investigation and breeding programme of cornelian cherry fruit in the Czech Republic

Valency of rare earths in RIn3 and RSn3: Ab initio analysis of electric-field gradients

In RIn3 and RSn3 the rare earth (R) is trivalent, except for Eu and Yb, which are divalent. This was experimentally determined in 1977 by perturbed angular correlation measurements of the electric-field gradient on a 111Cd impurity. At that time, the data were interpreted using a point charge model, which is now known to be unphysical and unreliable. This makes the valency determination potentially questionable. We revisit these data, and analyze them using ab initio calculations of the electric-field gradient. From these calculations, the physical mechanism that is responsible for the influence of the valency on the electric-field gradient is derived. A generally applicable scheme to interpret electric-field gradients is used, which in a transparent way correlates the size of the field gradient with chemical properties of the system.Comment: 10 page

High Field Magnetization of a NdCu2 Single Crystal

Studies of the high-field magnetization on a single crystal of NdCu2 with the field along the three principal crystallographic directions are presented. A crossing of the magnetization curves along the a- and b-axes is observed. The order of magnetization along each axis in high magnetic fields is then (μc < μb < μa). This behaviour is discussed in terms of a microscopic hamiltonian including crystal-field and Zeeman interactions. © 1995.This work was financially supported by 'Stichting voor Fundamenteel Onderzoek der Materie', the Charles University Grant Agency (Project 288), the Grant Agency of the Czech Republic (Project 202/93/0184) and Department of Energy of USA

The superconducting ferromagnet UCoGe

The correlated metal UCoGe is a weak itinerant ferromagnet with a Curie temperature T_C = 3 K and a superconductor with a transition temperature T_s = 0.6 K. We review its basic thermal, magnetic - on the macro and microscopic scale - and transport properties, as well as the response to high pressure. The data unambiguously show that superconductivity and ferromagnetism coexist below T_s = 0.6 K and are carried by the same 5f electrons. We present evidence that UCoGe is a p-wave superconductor and argue that superconductivity is mediated by critical ferromagnetic spin fluctuations.Comment: 19 pages; review paper; accepted for publication in the Journal of Low Temperature Physics (Special issue: Quantum Phase Transitions 2010

Neutron scattering study of magnetic order in single-crystalline CeCuAl 3_{3}

The CeTX3 compounds belong to the intensively studied group of materials revealing such properties asvalence fluctuations, heavy-fermion behavior, or pressure-induced superconductivity. So far, magnetic structurewas investigated in only a few of these.We performed a series of neutron-diffraction experiments on a structurallywell-defined CeCuAl3 single crystal. The ordered non-centro-symmetric tetragonal BaNiSn3-type (I4mm) crystalstructure as well as the antiferromagnetic order below TN ≈ 2.7 K were corroborated by our diffractionexperiments. The amplitude modulated magnetic structure with in-plane magnetic moments described by thepropagation vector k = (0.4, 0.6, 0) was revealed. The relation between structural parameters and magneticstructures in the family of isostructural CeTX3 compounds is discussed