Enhanced Antiferromagnetic Exchange between Magnetic Impurities in a Superconducting Host

It is generally believed that superconductivity only weakly affects the indirect exchange between magnetic impurities. If the distance r between impurities is smaller than than the superconducting coherence length $(r \lesssim \xi)$ , this exchange is thought to be dominated by RKKY interactions, identical to the those in a normal metallic host. This perception is based on a perturbative treatment of the exchange interaction. Here, we provide a non-perturbative analysis and demonstrate that the presence of Yu-Shiba-Rusinov bound states induces a strong $1/r^2$ anti-ferromagnetic interaction that can dominate over conventional RKKY even at distances significantly smaller than the coherence length $(r\ll \xi )$. Experimental signatures, implications and applications are discussed.Physic

A Versatile Software for Statistical Data Analysis and Spatial Correlation

Development of new tools for interpreting of and maximizing the amount of information extracted from georeferenced experimental and observational data remains an important task of computational geoscience. One of powerful tools for data analysis is the examination of correlation dependence between different, sometimes seemingly unrelated parameters. However, the correlation analysis of geospatial data can often be hampered by inadequate sampling or lack of coincidence between coordinates in the compared datasets. The number and capabilities of affordable software that can be used for these purposes are limited. Here we present a versatile software package for correlation analysis of spatial geo-referenced data with an additional set of tools. The software is implemented as a web service and contains a toolset for performing a geographic coordinate conversion, data interpolation, mapping, spatial correlation, data visualization and other auxiliary functions for spatial data analysis. The performance of the software is checked and confirmed on the real data. We call this service “UNCORR”—the UNiversal CORRelation tool

Pressure-induced polar phases in relaxor multiferroic PbFe0.5Nb0.5O3PbFe_{0.5}Nb_{0.5}O_{3}

The structural, magnetic, and vibrational properties of PbFe0.5Nb0.5O3 relaxor multiferroic have been studied by means of x-ray, neutron powder diffraction, and Raman spectroscopy at pressures up to 30 GPa. Two successive structural phase transitions from the initial R3m polar phase to Cm and Pm monoclinic polar phases were observed at P = 5.5 and 8.5 GPa. Both transitions are associated with anomalies in pressure behavior of several stretching and bending modes of oxygen octahedra as well as Fe/Nb localized vibrationalmodes. The G-type antiferromagnetic order remains stable upon compression up to 6.4 GPa, assuming possible multiferroic properties of pressure-induced phases. The Neel temperature increases with a pressure coefficient ´(1/TN)dTN/dP = 0.012 GPa−1. The observed pressure-induced phenomena in PbFe0.5Nb0.5O3 are in drasticcontrast with conventional multiferroics, exhibitin

An intermediate antipolar phase in NaNbO3NaNbO_{3} under compression

The crystal structure and vibration spectra of sodium niobate NaNbO$_3$ have been studied by means of neutron diffraction, X-ray diffraction and Raman spectroscopy at high pressures. An isostructural phase transformation from the initial antiferroelectric phase to an intermediate antiferroelectric phase HP-I have been observed under 2 GPa. This transformation is caused by complex reorientations of NbO$_6$ octahedra. Subsequent structural phase transition from the phase HP-I to an orthorhombic phase HP-III have been detected at pressures above 10 GPa. This transition leads to suppression of an antiferroelectric state of NaNbO$_3$. The observed phase transitions are accompanied by anomalies in lattice parameters compression

Structural, magnetic and vibrational properties of multiferroic GaFeO3GaFeO_{3} at high pressure

The crystal, magnetic structure and vibrational spectra of multiferroic GaFeO$_3$ have been studied by means of neutron, X-ray powder diffraction and Raman spectroscopy at pressures up to 6.2 and 42 GPa, respectively. A presence of Fe/Ga antisite disorder leads to a formation of the ferrimagnetic ground state with the Néel temperature T$_N$ = 292 K at ambient pressure. Upon compression, the magnetic ground state symmetry remains the same and the Néel temperature increases with a pressure coefficient (1/T$_N$)(dT$_N$/dP) = 0.011(1) GPa$^{−1}$. Application of high pressure above 21 GPa leads to a gradual structural phase transition from the polar orthorhombic Pc2$_1$n phase to nonpolar orthorhombic Pbnm phase. It is accompanied by anomalies in the pressure behaviour of several Raman modes. Pressure dependencies of lattice parameters and Raman modes frequencies in the observed structural phases were obtained

A Tribute to Sergey Odinokov

“My main goal was to point out new phenomena and spread the ideas, which will become the starting points for new research” [...

A Tribute to Sergey Odinokov

“My main goal was to point out new phenomena and spread the ideas, which will become the starting points for new research” [...

L’Europe orientale, 1650-1730. Crises, conflits et renouveau

Vers 1650, la Russie prend résolument position sur l’échiquier européen, où elle revendique le statut d’empire, à égalité avec celui des Habsbourg. C’est chose faite, ou à peu près, en 1730, au terme d’un long processus où jeu diplomatique, conflits armés, échanges culturels avec l’Occident et violentes révoltes à l’intérieur coexistent ou se succèdent. C’est cet ensemble d’événements, vus tantôt du côté de la Moscovie, tantôt du côté de ses voisins, qu’éclairent les articles réunis dans ce volume. Ils le font avant tout en s’attaquant aux stéréotypes, à l’aide parfois de sources inattendues, voire inconnues des spécialistes, comme les lettres de l’hetman cosaque Dorošenko au grand-vizir de la Sublime Porte ou l’unique exemplaire d’un pénitentiel prévu pour la confession du tsar. Russes xénophobes ? Peut-être, mais ce n’est pas ce qui ressort de la correspondance entre un marchand anglais et son professeur de russe. Nobles serviles ? Mais presque tous les auteurs de « projets », en 1730, rêvent d’une constitution analogue à celle de la Pologne-Lituanie. Les streltsy insurgés défendent-ils la Vieille Foi ou réclament-ils, plus prosaïquement, leur solde ? Sur un point tout au moins le succès de Pierre le Grand est indéniable : l’isolement de l’ancienne Russie appartient désormais au passé