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The orthorhombic monochalcogenide SnSe has attracted much attention in recent years as a promising high-temperature thermoelectric material. We present a study of its thermal conductivity and specific heat of SnSe between 2 K and 300 K and quantify its anisotropic thermal diffusivity, D. For both crystallographic orientations, thermal diffusivity remains above the recently identified Planckian limit (D > v 2 s τP , where vs is the sound velocity and τP = /kBT ) and its anisotropy in D is set by the anisotropy of vs. Comparison with cubic members of the IV-VI family leads to a consistent picture, where the diffusivity in all members of the family is set by the product of vs, τP and the 'melting' velocity derived from the melting temperature.

A systematic study of the superconducting properties in a series of arc-melted Nb-B samples close to the 1:1 composition was carried out. Powder X-ray diffraction (XRD) shows that all samples are both non-stoichiometric, and comprising of two crystal phases: a majority orthorhombic NbB-type phase, and traces of a minor body-centered cubic Nb-rich phase Nbss with stoichiometry close to Nb0.98B0.02. The emergence of superconductivity near Tc ∼ 9.0 K was inferred from magnetization data in chunk and powder samples. However, the very small superconducting volume fractions are inconsistent with superconductivity arising from the major NbB phase. On the other hand, micrographs of selected samples clearly show that the minority Nbss forms a three-dimensional network of filaments that meander around the grains of the majority phase, forming a percolation path. Here we report the superconductivity of the Nbss phase, and argue that the low superconducting volume fraction of non-stoichiometric NbB and zero resistance are due to the filaments of the minority phase. The electronic contribution to the entropy of the superconducting state, yielded from an analysis using the alpha model for single-band systems, indicates that the Sommerfeld constant of the arc-melted samples is close to the values found in non-superconducting NbB. Micrograph, XRD, and bulk measurements of magnetization, electrical resistivity, and specific heat suggest that the superconducting state in the NbB samples bearing some Nbss minority phase is due to the latter.

We have performed a systematic study of the physical properties and electronic structure of SrTiO 3 , SrTi 0.5 Ru 0.5 O 3 , and SrRuO 3. For the mixed compound, the temperature dependence of the magnetization is consistent with the occurrence of RuTi and TiRu defects. Despite being a semiconductor, the behavior of the electrical resistivity as a function of temperature is compatible with the emergence of small metallic regions richer in Ru concentration, a feature supported by the finite spectral weight at the Fermi level observed in the valence-band x-ray photoemission spectroscopy spectrum. The x-ray photoemission and absorption spectra of the SrTi 0.5 Ru 0.5 O 3 compound were simulated by double cluster model calculations, which include the TiO 6-RuO 6 interaction, and also by the linear combination of single cluster calculations for SrTiO 3 and SrRuO 3. The results indicate that the interaction between different octahedra may give rise to distinct peak characters, depending on the experimental spectrum being calculated. We argue that these effects are only captured with the explicit inclusion of the Ti-Ru interaction.

Rare-earth tetraborides RB4 are of great interest due to the occurrence of geometric magnetic frustration and corresponding unusual magnetic properties. While the Gd3+ spins in GdB4 align along the ab plane, Er3+ spins in the isomorphic ErB4 are confined to the c–axis. The magnetization in the latter exhibits a plateau at the midpoint of the saturation magnetization. Therefore, solid solutions of (Gd, Er)B4 provide an excellent playground for exploring the intricate magnetic behavior in these compounds. Single crystals of Gd(1-x)Erx B4 (x = 0, 0.2, and 0.4) were grown in aluminum flux. X-ray diffraction scans revealed single phase materials, and a drop in the unit cell volume with increasing Er content, suggesting the partial substitution of Er at the Gd sites. Heat capacity measurements indicated a systematic decrease of the Néel temperature (TN) with increasing Er content. The effective magnetic moment determined from the magnetization measurement agreed with the calculated free-ion values for Gd3+ and Er3+, providing further evidence for the successful substitution of Er for Gd. The partial substitution resulted in an anomalous ferromagnetic phase below TN, exhibiting significant anisotropy, predominantly along the c-axis. This intriguing behavior merits further studies of the magnetism in the Gd(1-x)ErxB4 borides.

Rare-earth tetraborides RB4 are of great interest due to the occurrence of geometric magnetic frustration and corresponding unusual magnetic properties. While the Gd3+ spins in GdB4 align along the ab plane, Er3+ spins in the isomorphic ErB4 are confined to the c–axis. The magnetization in the latter exhibits a plateau at the midpoint of the saturation magnetization. Therefore, solid solutions of (Gd, Er)B4 provide an excellent playground for exploring the intricate magnetic behavior in these compounds. Single crystals of Gd1−xErxB4 (x = 0, 0.2, and 0.4) were grown in aluminum flux. X-ray diffraction scans revealed single-phase materials, and a drop in the unit cell volume with increasing Er content, suggesting the partial substitution of Er at the Gd sites. Heat capacity measurements indicated a systematic decrease of the Néel temperature (TN) with increasing Er content. The effective magnetic moment determined from the magnetization measurement agreed with the calculated free ion values for Gd3+ and Er3+, providing further evidence for the successful substitution of Er for Gd. The partial substitution resulted in an anomalous ferromagnetic phase below TN, exhibiting significant anisotropy, predominantly along the c-axis. This intriguing behavior merits further studies of the magnetism in the Gd1−xErxB4 borides.

A preliminary study of the magnetic relaxation in (Bi, Pb)-2223 superconducting ceramics doped with α-Al2O3 nanoparticles is presented, taking as starting point the measurements of the M(t) dependence, both in samples in the form of powder as in pellet. The relaxation of the three types of vortices that can exist inside these materials is analyzed, emphasizing on the intragranular regionwhere the planar defects exist and, consequently, Abrikosov-Josephson vortices emerge. Finally, interesting results of the comparison between the behavior of the samples in the form of powder and in the form of pellet are shown from the estimation of the pinning energy of the vortices.