We report the crystal structure and highly anisotropic magnetic, transport, and thermal properties of an exceptionally good single crystal of U(Ru 0.92 Rh 0.08 ) 2 Si 2 , prepared using a modified Czochralski method. Our study, that also includes neutron diffraction results, shows all the heavy-fermion signatures of pristine URu 2 Si 2 ; however, the superconductivity, hidden order, and remnant weak antiferromagnetic orders are absent. Instead, the ground state of the doped system can be classified as a spin liquid that preserves the heavy-fermion character. U(Ru 0.92 Rh 0.08 ) 2 Si 2 exhibits a short-range magnetic order distinguished by reflections of a Lorentzian profile at q III = ( ) positions that disappear above ∼15 K. The short-range order seems to be a precursor of a long-range magnetic order that occurs with higher Rh concentration. We indicate that these short-range fluctuations involve, at least partially, inelastic scattering processes.
To study the influence of the sample preparation procedure on the superconducting properties of FeSe x Te 1−x , we have grown two FeSe 0.4 Te 0.6 crystals and investigated their superconducting properties. One of the crystals possessed a secondary phase of Fe 3 Se 2.1 Te 1.8 , while the other was a high-quality FeSe 0.4 Te 0.6 single crystal. We have checked the sample compositions and phases via energy dispersive x-ray spectroscopy to obtain a more sophisticated picture of the inclusions. Our susceptibility measurements under hydrostatic pressure show that neither pressure up to 9 kbar nor stress is sufficient to obtain a superconducting state in the homogeneous crystal. The critical temperature of two-phase FeSe 0.4 Te 0.6 increases at 8.9 kbar from 12.3 K to T c =17.9 K. Therefore, we conclude that inhomogeneities are a necessary feature for providing superconductivity in this iron chalcogenide system. We have prepared Fe 3 Se 2.1 Te 1.8 polycrystals and studied their magnetic properties for comparison.
In a ferroelectric helimagnetic phase of a spin-driven multiferroic CuFeO2, we have found irreversibly additive evolution of electric polarization (P ) induced by sweeping magnetic field (H) under an applied electric field (E), despite a large coercive electric field in the phase. From the unpolarized neutron diffraction experiments with in-situ P measurements under applied E, we have revealed that increment of P is achieved by the variation of an incommensurate magnetic modulation wave number (q) of the helical magnetic ordering in H-sweeping regardless of increasing or decreasing H. Combining this result with H dependence of the magnetic diffraction intensity and a result of off-bench P measurements, we conclude that the H evolution of P is caused by a change in a (ferroelectric) helicity domains volume fraction by driving the helicity domain wall (DW). Taking into account the results of further detailed P measurements, we propose a possible model of the phenomenon that, instead of simply driving the helicity DW, the variation of q causes the neighborhood of the helicity DWs to store an extra exchange energy and to be sensible for E, and then, these regions and the helicity DWs are reconstructed by applied E so as to enlarge the helicity domain favored by the direction of E. The present study demonstrates the magneto-electric cross correlation in driving multiferroic DW: we could activate the frozen ferroelectric DW by means of H-sweeping. This is also an achievement of driving an antiferromagnetic DW, which is difficult in conventional antiferromagnets in principle.
Abstract. In this work, we present low temperature magnetic and electronic properties measured on selected Kramers rare-earth oxychlorides REOCl, RE= Nd, Gd, Dy which adopt the PbFCl-type of structure. Prepared powder samples were characterized by means of standard structural, magnetic and electronic methods as X-ray diffraction (300 K), heat capacity (0.3 K -12 K) and susceptibility measurements (2 K -300 K, at ambient pressure and hydrostatic pressures up to 0.68 ± 0.01 GPa). Our results indicate new transition to the ordered magnetic state for GdOCl and NdOCl compound at temperatures of 5 K and 1.5 K, respectively. We found small increase of magnetization saturation value of dysprosium oxychloride with an applied hydrostatic pressure, but no remarkable changes occur to antiferromagnetic transition temperature (T N ∼ 9.2 K) when a moderate hydrostatic pressure (p ≤ 0.68 ± 0.01 GPa) was applied. Observed deviations from the Curie Weiss behavior below 26 K can be caused by the vicinity of the magnetic ordering temperature, or another magnetic effects. The single crystal experiments which will solve this opened question are in progress.
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