54 research outputs found
Magnetization, crystal structure and anisotropic thermal expansion of single-crystal SrEr2O4
The magnetization, crystal structure, and thermal expansion of a nearly
stoichiometric SrErO single crystal have
been studied by PPMS measurements and in-house and high-resolution synchrotron
X-ray powder diffraction. No evidence was detected for any structural phase
transitions even up to 500 K. The average thermal expansions of lattice
constants and unit-cell volume are consistent with the first-order Gr\"uneisen
approximations taking into account only the phonon contributions for an
insulator, displaying an anisotropic character along the crystallographic
\emph{a}, \emph{b}, and \emph{c} axes. Our magnetization measurements indicate
that obvious magnetic frustration appears below 15 K, and
antiferromagnetic correlations may persist up to 300 K.Comment: 6 pages, 5 figure, 2 table
CHIME : Cross-passage hierarchical memory network for generative review question answering
We introduce CHIME, a cross-passage hierarchical memory network for question answering (QA) via text generation. It extends XLNet introducing an auxiliary memory module consisting of two components: the context memory collecting cross-passage evidences, and the answer memory working as a buffer continually refining the generated answers. Empirically, we show the efficacy of the proposed architecture in the multi-passage generative QA, outperforming the state-of-the-art baselines with better syntactically well-formed answers and increased precision in addressing the questions of the AmazonQA review dataset. An additional qualitative analysis revealed the interpretability introduced by the memory module
Incommensurate antiferromagnetic order in the manifoldly-frustrated SrTbO with transition temperature up to 4.28 K
The Nel temperature of the new frustrated family of
Sr\emph{RE}O (\emph{RE} = rare earth) compounds is yet limited to
0.9 K, which more or less hampers a complete understanding of the
relevant magnetic frustrations and spin interactions. Here we report on a new
frustrated member to the family, SrTbO with a record =
4.28(2) K, and an experimental study of the magnetic interacting and
frustrating mechanisms by polarized and unpolarized neutron scattering. The
compound SrTbO displays an incommensurate antiferromagnetic (AFM) order
with a transverse wave vector \textbf{Q} = (0.5924(1),
0.0059(1), 0) albeit with partially-ordered moments, 1.92(6) at
0.5 K, stemming from only one of the two inequivalent Tb sites mainly by virtue
of their different octahedral distortions. The localized moments are confined
to the \emph{bc} plane, 11.9(66) away from the \emph{b} axis probably
by single-ion anisotropy. We reveal that this AFM order is dominated mainly by
dipole-dipole interactions and disclose that the octahedral distortion,
nearest-neighbour (NN) ferromagnetic (FM) arrangement, different next NN FM and
AFM configurations, and in-plane anisotropic spin correlations are vital to the
magnetic structure and associated multiple frustrations. The discovery of the
thus far highest AFM transition temperature renders SrTbO a new
friendly frustrated platform in the family for exploring the nature of magnetic
interactions and frustrations.Comment: 19 pages, 8 Figures, 1 Tabl
Distinct itinerant spin-density waves and local-moment antiferromagnetism in an intermetallic ErPd2 Si2 single crystal
Identifying the nature of magnetism, itinerant or localized, remains a major challenge in condensed-matter science. Purely localized moments appear only in magnetic insulators, whereas itinerant moments more or less co-exist with localized moments in metallic compounds such as the doped-cuprate or the iron-based superconductors, hampering a thorough understanding of the role of magnetism in phenomena like superconductivity or magnetoresistance. Here we distinguish two antiferromagnetic modulations with respective propagation wave vectors at Q± = (H ± 0.557(1), 0, L ± 0.150(1)) and QC = (H ± 0.564(1), 0, L), where (H, L) are allowed Miller indices, in an ErPd2Si2 single crystal by neutron scattering and establish their respective temperature- and field-dependent phase diagrams. The modulations can co-exist but also compete depending on temperature or applied field strength. They couple differently with the underlying lattice albeit with associated moments in a common direction. The Q± modulation may be attributed to localized 4f moments while the QC correlates well with itinerant conduction bands, supported by our transport studies. Hence, ErPd2Si2 represents a new model compound that displays clearly-separated itinerant and localized moments, substantiating early theoretical predictions and providing a unique platform allowing the study of itinerant electron behavior in a localized antiferromagnetic matrix
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