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We combine photometry of Eris from a 6-month campaign on the Palomar 60-inch telescope in 2015, a 1-month Hubble Space Telescope WFC3 campaign in 2018, and Dark Energy Survey data spanning 2013--2018 to determine a light curve of definitive period $15.771\pm 0.008$~days (1-$\sigma$ formal uncertainties), with nearly sinusoidal shape and peak-to-peak flux variation of 3\%. This is consistent at part-per-thousand precision with the $P=15.78590\pm0.00005$~day period of Dysnomia's orbit around Eris, strengthening the recent detection of synchronous rotation of Eris by Szakats et al (2022) with independent data. Photometry from Gaia is consistent with the same light curve. We detect a slope of $0.05\pm0.01$~mag per degree of Eris' brightness with respect to illumination phase, intermediate between Pluto's and Charon's values. Variations of $0.3$~mag are detected in Dysnomia's brightness, plausibly consistent with a double-peaked light curve at the synchronous period. The synchronous rotation of Eris is consistent with simple tidal models initiated with a giant-impact origin of the binary, but is difficult to reconcile with gravitational capture of Dysnomia by Eris., Comment: Submitted to Planetary Science Journal

We present a study on the magnetic susceptibility $\chi(T)$ and electrical resistance, as a function of temperature and magnetic field $R(T,H)$, of the ferromagnetic heavy fermion YbNi$_2$. The X-ray diffraction analysis shows that the synthesized polycrystalline samples crystallizes in the cubic Laves phase structure C15, with a spatial group $Fd\overline{3}m$. The magnetic measurements indicate a ferromagnetic behavior with transition temperature at 9 K. The electrical resistance is metallic-like at high temperatures and no signature of Kondo effect was observed. In the ferromagnetic state, the electrical resistance can be justified by electron-magnon scattering considering the existence of an energy gap in the magnonic spectrum. The energy gap was determined for various applied magnetic fields. Magnetoresistance as a function of applied magnetic field, subtracted from the $R(T,H)$ curves at several temperatures, is negative from 2 K until about 40 K for all applied magnetic fields. The negative magnetoresistance originates from the suppression of magnetic disorder by the magnetic field., Comment: 11 pages, 6 figures, accepted in J. Supercond. Nov. Magn

Crystal structure, thermal and magnetic properties were systematically studied in the Y$_{1-x}$Pr$_x$CrO$_3$ with $0 \leq x \leq 0.3$ compositions. Magnetic susceptibility and specific heat measurements show an increase of the antiferromagnetic transition temperature ($T_N$) as Pr is substituted in the Y sites and notable magnetic features are observed below $T_N$. Strong coupling between magnetic and crystalline parameters is observed in a small range of Pr compositions. A small perturbation in the lattice parameters by Pr ion is sufficient to induce a spin reorientation transition followed by magnetization reversal, to finally induce exchange bias effect. The spin reorientation temperature ($T_{SR}$) is increased from 35 K to 149 K for $0.025 \leq x \leq 0.1$ compositions. It is found that the Cr spins sublattice rotates continuously from $T_{SR}$ to a new spin configuration a lower temperature. In addition, magnetization reversal is observed at $T^* \sim 35$ K for x= 0.05 up to $T^* \sim 63$ K for x = 0.20 composition. The $M-H$ curves show negative exchange bias effect induced by Pr ions, which are observed below of 100 K and being more intense at 5 K. At 10 K, the magnetic contribution of the specific heat, as well as the ZFC magnetization, show the rise of a peak with increasing Pr content. The magnetic anomaly could be associated with the freezing of the Pr magnetic moment randomly distributed at the 4c crystallographic site. A clear correspondence between spin reorientation, magnetization reversal and exchange bias anisotropy with the tilting and octahedral distortion is also discussed., Comment: 14 pages, 12 figures, to be published in Physical Review Materials

We studied the effects of substitution of Pd by Cu on the upper critical field of the noncentrosymmetric superconductor Li$_2$Pd$_{3-x}$Cu$_x$B, with x=0.0, 0.1 and 0.2. The upper critical field as a function of temperature was determined by resistance measurements at different magnetic fields. We found that the superconducting transition temperature decreases as the Cu content increases. Moreover, the temperature dependence of the upper critical field is linear in the range of the temperature studied and, at low temperature, is enhanced compared with the prediction of the Werthamer-Helfan-Hohenberg theory. This indicates that the breaking of Cooper pairs by spin orbit scattering and Pauli paramagnetism is negligible, and that the upper critical field enhancement is mainly because the electron-phonon coupling and disorder., Comment: 6 pages, 4 figures. Accepted in Solid State Communications

We study the crystalline and electronic properties of the $\textrm{Fe}_{1-x}\textrm{Co}_x\textrm{Se}$ system ($x=0$, 0.25, 0.5, 0.75, and 1.0) using X-ray diffraction, X-ray spectroscopy and density functional theory. We show that the introduction of Co $3d$ states in FeSe relaxes the bond strengths and induces a structural transition from tetragonal to hexagonal whose crossover takes place at $x\approx0.38$. This structural transition in turn modifies the magnetic order which can be related to the spin state. Using resonant inelastic X-ray spectroscopy we estimate the spin state of the system; FeSe is found to be in a high spin state (S=2), but Fe is reduced to a low spin state upon Co substitution of $x \le 0.25$, well below the structural transition. Finally, we show evidence that FeSe is a moderately correlated system but the introduction of Co into the host lattice weakens the correlation strength for $x\ge0.25$. These novel findings are important to unravel the mechanisms responsible for the superconducting state in iron-chalcogenide superconductors., Comment: 10 pages, 4 figures, to be published in PRB

Polycrystalline samples of LaFeO3 and GdFeO3 were synthesized by the molten salt method. Some properties and the quality of the resulting compounds were investigated. The crystal structure and purity of the samples was determined through X-ray diffraction and Rietveld analysis. The vibrational properties were characterized by Raman and IR spectroscopy. M\"ossbauer spectroscopy was used to determine the ionic state of the Fe ions and the internal hyperfine magnetic fields Considerable reduction of the heat treatment (temperature and time) for the reaction to take place was achieved without detriment of the quality of the compounds., Comment: 10 figures

We study the electronic properties of the $\textrm{Fe}\textrm{Se}_{1-x}\textrm{Te}_x$ system ($x=0$, 0.25, 0.5, 0.75, and 1) from the perspective of X-ray spectroscopy and density functional theory (DFT). The analysis performed on the density of states reveals marked differences in the distribution of the $5p$ states of Te for $x>0$. We think that this finding can be associated with the fact that superconductivity is suppressed in FeTe. Moreover, using resonant inelastic X-ray scattering, we estimate the spin state of our system which can be correlated to the magnetic order. We find that the spin state of the $\textrm{Fe}\textrm{Se}_{1-x}\textrm{Te}_x$ system fluctuates, as a function of $x$, between $S=0$ and $S=2$ with Fe in FeSe in the highest spin state. Finally, our DFT calculations nicely reproduce the X-ray emission spectra performed at the Fe $L$-edge (which probe the occupied states) and suggest that the $\textrm{Fe}\textrm{Se}_{1-x}\textrm{Te}_x$ system can be considered at most as a moderately correlated system., Comment: 5 figures, 27 pages. Article accepted in The Journal of Physical Chemistry C

The effects of Ca substitutions on the structure, magnetism and electrical properties of YCrO3 ceramics are investigated by X-ray diffraction, magnetic susceptibility and electrical conductivity measurements. The cell volume decrease occurs through the change from Cr(III) to Cr(IV) as a result of the charge compensation of the Ca doping. No changes are observed in the antiferromagnetic transition temperature while strong changes are observed in the transport measurements due to Ca content. The increase of the electrical conductivity as well as the decrease of the activation energy are caused by the formation of the small-polarons localized in the O-Cr-O lattice distortion. The origin of small-polarons in the undoped sample is different in nature from the calcium doped. "Local non-centrosymetry" is the source of the small-polaron formation in undoped sample, while the change from Cr(III) to Cr(IV) through the charge compensation of Ca(II) in the Y(III) site is the source of small-polarons formations. The decrease of the average bond length Cr-O as well as effective moments in the paramagnetic state and the increase of the electrical conductivity are clear evidence that the Ca doping induces localized polarons, which in turn, these quasiparticles move from site to site by a thermally activated process in the doped YCrO3 compound. Here, we also discuss a possible mechanism of small-polaron injections in YCrO3 matrix., Comment: 17 pages, 6 figures, acepted in Mater. Chem. Phys

ZnO nanoparticles with Wurtzite structure were prepared by chemical methods at low temperature in aqueous solution. Nanoparticles are in the range from about 10 to 30 nm. Ferromagnetic properties were observed from 2 K to room temperature and above. Magnetization vs temperature, M(T) and isothermal measurements M(H) were determined. The coercive field clearly shows ferromagnetism above room temperature. The chemical synthesis, structural defects in the bulk related to oxygen vacancies are the main factors for the observed magnetic behavior. PACS numbers: 61.46.Hk Nanocrystals, 75.50.Pp Magnetic semiconductors, 81.05.Dz II-VI semiconductors

Polycrystalline samples of FeSe1-xTex (x = 0.00, 0.25, 0.50, 0.75 and 1.00) were synthesized by solid-state reaction to study the effects of substituting Se with Te in the system. The magnetization properties of the resulting compounds were investigated and the crystallographic structures of the samples analyzed through X-ray diffraction. Moessbauer spectroscopy was used to determine the ionic state of the Fe ions and the hyperfine fields. The magnetic susceptibility curves of the samples with x = 0.25, 0.50 and 0.75 show superconducting behavior. The lattice parameters and the cell volume increase monotonically with increasing Te concentration and the Moessbauer spectra reveal the absence of internal magnetic hyperfine fields., Comment: Eighteen pages, six figures, two tables

The results of the muon-spin rotation experiments on BCS superconductors NbB_2+x (x = 0.2, 0.34) are reported. Both samples, studied in the present work, exhibit rather broad transitions to the superconducting state, suggesting a distribution of the volume fractions with different transition temperatures (T_c)'s. By taking these distributions into account, the dependence of the inverse squared zero-temperature magnetic penetration depth (\lambda_0^{-2}) on T_c was reconstructed for temperatures in the range 1.5K

Samples of the Ru1-xFexSr2GdCu2O8 system with x = 0, 0.025, 0.05, 0.075, 0.1 and 0.2, were prepared and their structural, superconducting and magnetic properties were studied. Rietveld refinement of the X-ray diffraction patterns show that the Fe substitution occurs in both Ru and Cu sites. An increase of Fe concentration produces no significant changes in the bond angle Ru-O(3)-Ru, which is a measure of the rotation of the RuO6 octahedra around the c-axis, and also in the bond angle Ru-O(1)-Cu, which is a measure of the canting of the RuO6 octahedra. On the other hand, the bond angle Cu-O(2)-Cu, which is a measure of the buckling of the CuO2 layer, has a slight tendency to decrease with the increase of the Fe content. We found thet both ferromagnetic and superconducting transition temperatures are reduced with the increase of Fe concentration. Analisys related to the decay of the superconducting and ferromagnetic states is presented., Comment: 9 pages, 7 figures

The effects of Co substitution on structural and superconducting properties of RuSr2GdCu2O8 compound have been studied. Rietveld refinements of the X-ray diffraction patterns indicate that the cobalt ion progressively replaces ruthenium sites. This replacement induces significant changes on the crystal structure and on the magnetic and superconducting properties. The effects Co substitution on the superconducting behaviour, and more particulary on the changes induce by the hole doping mechanism, were investigated in (Ru1-xCox)Sr2GdCu2O8 by a "bond valence sum" analysis with Co content from x= 0.0 to x = 0.2. The weak ferromagnetic transition at Tm= 138.2 K is shifted to lower temperature, and suppressed at higher Co content. From the crystallographic point of view the Ru-O(1)-Cu bond angle, associated to the rotation of the RuO6 octahedra, around the c-axis remain essetially constant when Ru is substituted by Co. Furthermore, increasing Co content has the effect to increase the weak ferromagnetic moment, which may be interpreted as the main responsible for breaking the delicate balance between magnetic and superconducting ordering., Comment: 21 pages, 8 figures