Pressure effect on the Fermi surface and electronic structure of LuGa₃ and TmGa₃

The Fermi surfaces and cyclotron masses of LuGa₃ and TmGa₃ compounds are studied by means of the de Haas—van Alphen effect technique under pressure. The highly anisotropic pressure dependences of the de Haas—van Alphen frequencies and cyclotron masses have been observed in both compounds. Concurrently, the ab initio calculations of the volume-dependent band structures have been carried out for these compounds, including ferromagnetic configuration phase of TmGa₃, by employing a relativistic version of the full-potential linear muffin-tin orbital method within the local spin-density approximation. The experimental data have been analysed on the basis of the calculated volume-dependent band structures and compared with the corresponding pressure effects in the isostructural compound ErGa₃

Magnetic structure of antiferromagnetic NdRhIn5

The magnetic structure of antiferromagnetic NdRhIn5 has been determined using neutron diffraction. It has a commensurate antiferromagnetic structure with a magnetic wave vector (1/2,0,1/2) below T_N = 11K. The staggered Nd moment at 1.6K is 2.6mu_B aligned along the c-axis. We find the magnetic structure to be closely related to that of its cubic parent compound NdIn3 below 4.6K. The enhanced T_N and the absence of additional transitions below T_N for NdRhIn5 are interpreted in terms of an improved matching of the crystalline-electric-field (CEF), magnetocrystalline, and exchange interaction anisotropies. In comparison, the role of these competing anisotropies on the magnetic properties of the structurally related compound CeRhIn5 is discussed.Comment: 4 pages, 4 figure

Hall effect in the vicinity of quantum critical point in Tm1-xYbxB12

The angular, temperature and magnetic field dependences of Hall resistance roH for the rare-earth dodecaboride solid solutions Tm1-xYbxB12 have been studied in a wide vicinity of the quantum critical point (QCP) xC~0.3. The measurements performed in the temperature range 1.9-300 K on high quality single crystals allowed to find out for the first time in these fcc compounds both an appearance of the second harmonic contribution in ro2H at QCP and its enhancement under the Tm to ytterbium substitution and/or with increase of external magnetic field. When the Yb concentration x increases a negative maximum of a significant amplitude was shown to appear on the temperature dependences of Hall coefficient RH(T) for the Tm1-xYbxB12 compounds. Moreover, a complicated activation type behavior of the Hall coefficient is observed at intermediate temperatures for x>0.5 with activation energies Eg~200K and Ea~55-75K in combination with the sign inversion of RH(T) at low temperatures in the coherent regime. The density of states renormalization effects are analyzed within the variation of Yb concentration and the features of the charge transport in various regimes (charge gap formation, intra-gap manybody resonance and coherent regime) are discussed in detail in Tm1-xYbxB12 solid solutions.Comment: 38 pages including 10 figures, 70 reference

Orbital ordering phenomena in dd- and ff-electron systems

In recent decades, novel magnetism of $d$- and $f$-electron compounds has been discussed very intensively both in experimental and theoretical research fields of condensed matter physics. It has been recognized that those material groups are in the same category of strongly correlated electron systems, while the low-energy physics of $d$- and $f$-electron compounds has been separately investigated rather in different manners. One of common features of both $d$- and $f$-electron systems is certainly the existence of active orbital degree of freedom, but in $f$-electron materials, due to the strong spin-orbit interaction in rare-earth and actinide ions, the physics seems to be quite different from that of $d$-electron systems. In general, when the number of internal degrees of freedom and relevant interactions is increased, it is possible to obtain rich phase diagram including large varieties of magnetic phases by using several kinds of theoretical techniques. However, we should not be simply satisfied with the reproduction of rich phase diagram. It is believed that more essential point is to seek for a simple principle penetrating complicated phenomena in common with $d$- and $f$-electron materials, which opens the door to a new stage in orbital physics. In this sense, it is considered to be an important task of this article to explain common features of magnetism in $d$- and $f$-electron systems from a microscopic viewpoint, using a key concept of orbital ordering, in addition to the review of the complex phase diagram of each material group.Comment: 112 pages, 38 figure

High-resolution manometry in diagnostics and evaluation of therapy effectiveness in patients with eosinophilic esophagitis – underestimated breakthrough or dead end?

Eosinophilic esophagitis (EoE) is a chronic disease with non-specific symptoms, among which dysphagia is a prevailing one. The observed increase of EoE rate, its chronic and recurrent character, as well as invasive follow-up examination (periodical panendoscopy with specimen collection for histopathology), compel optimization of both the diagnostics algorithm and disease monitoring through searching for new, unique methods and tools so far not applied, including high-resolution manometry (HRM). Mentioned investigations result from advances in comprehension of disease pathogenesis, in which it is suggested that development of a chronic inflammatory reaction of the esophageal wall may lead to consecutive fibrosis and motility disorders. In research published to date one manometric pattern characteristic for EoE was not obtained, whereas the obtained inconsistent and at times contradictory results do not correlate either with symptoms exacerbation or endoscopic scan. Numerous constraints of discussed studies as well as current knowledge in disease etiopathology and esophagus biomechanics prompt further investigation of HRM significance in diagnostics and therapy monitoring of patients with EoE

f-Electron Behavior in Rare Earth Based Systems: Localization or Itinerancy?

Measurement of the two-dimensional angular correlation of the electron-positron annihilation radiation complemented with ab initio calculations can provide decisive information about the character of the f-electrons in rare earth compounds. We provide examples of f-electron localized and f-electron itinerant systems, respectively. (i) In the case of the antiferromagnetic heavy fermion and superconductor CeIn$\text{}_{3}$ the multisheet Fermi surface, reconstructed from our measurements in the paramagnetic phase, agrees closely with the predictions of band structure calculations regarding the Ce 4f electrons as fully localized. (ii) On the other hand, our studies of the antiferromagnet actinide based UGa$\text{}_{3}$ in the paramagnetic phase, compared with calculations which include the effects due to the non-uniform positron density and the electron-positron correlations, produce a substantial evidence that an unconstrained 5f-electron itinerant description applies

f-Electron Behavior in Rare Earth Based Systems: Localization or Itinerancy?

Measurement of the two-dimensional angular correlation of the electron-positron annihilation radiation complemented with ab initio calculations can provide decisive information about the character of the f-electrons in rare earth compounds. We provide examples of f-electron localized and f-electron itinerant systems, respectively. (i) In the case of the antiferromagnetic heavy fermion and superconductor CeIn$\text{}_{3}$ the multisheet Fermi surface, reconstructed from our measurements in the paramagnetic phase, agrees closely with the predictions of band structure calculations regarding the Ce 4f electrons as fully localized. (ii) On the other hand, our studies of the antiferromagnet actinide based UGa$\text{}_{3}$ in the paramagnetic phase, compared with calculations which include the effects due to the non-uniform positron density and the electron-positron correlations, produce a substantial evidence that an unconstrained 5f-electron itinerant description applies

Magnetization of NdIn3, GdIn3 and DyIn3 single crystals

L'aimantation de monocristaux de NdIn3, GdIn3 et DyIn3 a été mesurée suivant trois axes cristallographiques principaux dans le domaine antiferromagnétique ordonné, sous champ magnétique continu jusqu'à 19 T. On a observé sur DyIn3 un processus d'aimantation à plusieurs sauts attribué à la structure magnétique spécifique de ce compost. L'aimantation à saturation de NdIn3 et DyIn3 atteint des valeurs inférieures aux valeurs calculées pour les ions terres rares libres.The magnetization of NdIn3, GdIn3 and DyIn3 single crystals has been studied in the antiferromagnetically ordered state along three principal crystallographic axes in stationary magnetic fields up to 19 T. The multiple-step magnetization process has been found in DyIn3 due to its specific magnetic structure. Saturation magnetization of NdIn3 and DyIn3 reaches the values lower than those expected for free RE3+ ions