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Evidence for magnetic dimers and skyrmion lattice formation in Eu2Pd2Sn
No full textThe magnetic, thermal, and transport properties of the noncentrosymmetric compound Eu2Pd2Sn are reexamined
with the inclusion of detailed measurements. In its paramagnetic phase, the outstanding feature of
this compound is the formation of Eu2+ dimers, which allows us to understand the deviation of the magnetic
susceptibility χ(T ) from the Curie-Weiss law below about 70 K, the field-dependent magnetization M(B) below
≈80K, and the reduced entropy at the ordering temperature S(TN ) = 0.64R ln(8). A significant change in the
exchange interactions occurs between T ≈ 70K (where θP = 18K) and TN = 13.3K (to θP = −4.5K). The
strong electronic overlap, arising from the reduced Eu-Eu spacing (compared with that in pure Eu2+) is expected
to favor dimer quasiparticles formation, leading to a significant change in the magnetic structure. From the
analysis of the derivatives of the magnetic parameters, ∂χ/∂T and ∂M/∂B, as well as the field dependence of
the specific heat and mangnetoresistance, a comprehensive magnetic phase diagram is obtained. Two critical
points are recognized and a tentative description of the magnetic structures is proposed. The possible formation
of a skyrmion lattice, arising from the presence of magnetically frustrated pockets in the phase diagram, is
suggested by theoretical studies on hexagonal structures that exhibit similar interaction patterns
Phase equilibria and crystal structures in the ytterbium–copper–zinc system
No full textPhase equilibria in the isothermal section (600 °C) of the ytterbium-copper-zinc ternary system were determined over the entire concentration range by powder X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Extended substitutional Cu/Zn homogeneity regions are mainly formed from the Yb-Zn and Yb-Cu binary compounds. There are four ternary compounds, namely τ1-YbCu5−xZnx (cubic AuBe5 type, 0.7 < x ≤ 1.5), τ2-YbCu5−xZnx (hexagonal CaCu5 type, 1.8 ≤ x ≤ 4.4), τ3-Yb2CuZn7 and τ4-Yb5Cu2−xZn1+x. Magnetic measurements were performed for compositions along the phases τ1-YbCu5−xZnx and τ2-YbCu5−xZnx, as well as for the compound Yb33Cu50Zn17 belonging to the pseudobinary system YbCu2-YbZn2. While the Yb ion has a valence of 2 + for compositions ≥33% at% Yb, the Yb valence along the YbCu5−xZnx composition line is influenced by the crystal structure: Yb3+ for the cubic AuBe5 type and nonmagnetic Yb2+ for the hexagonal CaCu5 type
Incommensurate magnetic cycloidal order in noncentrosymmetric E u2 P d2Sn
No full textThe structural and magnetic properties of the noncentrosymmetric Eu2Pd2Sn compound have been investigated by synchrotron x-ray and neutron powder diffraction and Eu151 Mössbauer spectroscopy. No structural transition was observed in the temperature range 4-290 K. The magnetic phase that develops below ∼13.8(5) K is characterized by an incommensurate cycloidal ordering in the ac plane of the Eu substructure. This magnetic structure shows significant analogies to the structure observed in EuNiGe3, possibly indicating the occurrence of a skyrmion lattice for Eu2Pd2Sn as well
Crystal Structure and Magnetism of Noncentrosymmetric Eu2Pd2Sn
No full textThe new intermetallic compound Eu2Pd2Sn has been investigated. A single crystal was selected from the alloy and was analyzed by single-crystal X-ray diffraction, revealing that this compound possesses the noncentrosymmetric Ca2Pd2Ge structure type being, so far, the only rare-earth-based representative. Bonding analysis, performed on the basis of DOS and (I)COHP, reveals the presence of strong covalent Sn-Pd bonds in addition to linear and equidistant Pd-Pd chains. The incomplete ionization of Eu leads to its participation in weaker covalent interactions. The magnetic effective moment, extracted from the magnetic susceptibility χ(T) is μeff = 7.87 μB, close to the free ion Eu2+ value (μeff = 7.94 μB). The maximum of χ(T) at TN ∼13 K indicates an antiferromagnetic behavior below this temperature. A coincident sharp anomaly in the specific heat CP(T) emerges from a broad anomaly centered at around 10 K. From the reduced jump in the heat capacity at TN a scenario of a transition to an incommensurate antiferromagnetic phase below TN followed by a commensurate configuration below 10 K is suggested
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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