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Betancourth, D.; Correa, V. F.; Facio, J.I.; Fernández J.; Vildosola, V.; Lora-Serrano, R.; Cadogan, J.M.; Aligia, A.A.; Cornaglia, P.S.; García D.J. |
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Title |
Magnetostriction reveals orthorhombic distortion in tetragonal Gd compounds |
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2019 |
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Physical Review B |
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Phys. Rev. B |
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99 |
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134406 |
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We report detailed thermal expansion and magnetostriction experiments on GdCoIn5 and GdRh(In1−xCdx )5
(x = 0 and 0.025) single-crystal samples that show a sudden change in the dilation at a field B for temperatures
below the Néel transition temperature TN . We present a first-principles model including crystal-field effects,
dipolar and exchange interactions, and the dependence of the latter with lattice distortions in order to fully
account for the magnetostriction and magnetic susceptibility data. The mean-field solution of the model shows
that a transition between metastable states occurs at the field B. It also indicates that two degenerate phases
should coexist at temperatures below TN , which may explain the lack of observation, in high-resolution
x-ray experiments, of an orthorhombic distortion at the Néel transition, even though the experimentally
determined magnetic structure breaks the tetragonal symmetry and the magnetoelastic coupling from our model
is significant. These conclusions could be extended to other tetragonal Gd-based compounds that present the
same phenomenology. |
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BT @ victor.correa @ |
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815 |
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Bruchhausen, A.; Bahrs, S.; Fleischer, K.; Goni, A.R.; Fainstein, A.; Nieva, G.; Aligia, A.A.; Richter, W.; Thomsen, C. |
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Title |
Photoinduced chain-oxygen ordering in detwinned YBa2Cu3O6.7 single crystals studied by reflectance-anisotropy spectroscopy |
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Journal Article |
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2004 |
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PHYSICAL REVIEW B |
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69 |
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22 |
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224508 |
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We present a reflectance-anisotropy spectroscopy (RAS) investigation of photoexcitation and annealing effects in oxygen deficient detwinned YBa2Cu3O6.7 single crystals. Well-resolved RAS spectral features are either bleached or enhanced on a time scale of hours upon laser illumination with polarization parallel to the Cu(1)-O(1) chains. These photoinduced effects recover with room temperature annealing in the dark. Based on previous ellipsometric studies and on cluster models for the oxygen Cu-O(1) chain-fragments we are able to assign the RAS peaks that depend on illumination to optical transitions involving copper atoms located either on short chain-fragments or in isolated Cu-O(4)(2) sites. This provides strong evidence that photoinduced chain-oxygen ordering is indeed at the origin of persistent photoconductivity and Raman vibrational mode bleaching in these materials. |
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1098-0121 |
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ISI:000222530900070 |
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BT @ hernan @ |
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208 |
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Lobos, A.M.; Aligia, A.A.; Sereni, J.G. |
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Specific heat of magnetic Ce alloys within a two-component model |
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Journal Article |
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2004 |
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European Physical Journal B |
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Eur. Phys. J. B |
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41 |
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3 |
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289-294 |
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We propose a description of the electronic properties of Ce alloys as an inhomogeneous mixture of two components: one containing magnetic Ce ions with an RKKY interaction J(H) between them, and the other described as a collection of Kondo impurities with exchange interaction J(K). Both J(H) and J(K) are assumed to depend on a composition parameter X, with a Gaussian distribution around a value X-0 (near to the expectation value of X), related to the experimental composition parameter x of the alloy. When the concentration of the Kondo impurities is large, the specific heat C displays non-Fermi liquid behavior over a wide temperature range. The main qualitative features of C/T as a function of temperature T observed in several Ce alloys are reproduced using simple J(H)(X) and J(K)(X) dependences. |
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1434-6028 |
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ISI:000224753700002 |
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BT @ hernan @ |
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62 |
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Romero, M.A.; Aligia, A.A.; Sereni, J.G.; Nieva, G. |
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Title |
Interpretation of experimental results on Kondo systems with crystal field |
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2014 |
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Journal of Physics: Condensed Matter |
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J. Phys. : Condens. Matter |
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26 |
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025602 |
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cond-mat.str-el |
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We present a simple approach to calculate the thermodynamic properties of single Kondo impurities including orbital degeneracy and crystal field effects (CFE) by extending a previous proposal by K. D. Schotte and U. Schotte [Physics Lett. A 55, 38 (1975)]. Comparison with exact solutions for the specific heat of a quartet ground state split into two doublets shows deviations below $10\%$ in absence of CFE and a quantitative agreement for moderate or large CFE. As an application, we fit the measured specific heat of the compounds CeCu$2$Ge$2$, CePd${3}$Si${0.3}$, CePdAl, CePt, Yb$2$Pd$2$Sn and YbCo$2$Zn${20}$. The agreement between theory and experiment is very good or excellent depending on the compound, except at very low temperatures due to the presence of magnetic correlations (not accounted in the model). |
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arXiv:1308.3256v3; Journal Ref: J. Phys.: Condens. Matter 26 (2014) 025602 (9pp) |
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BT @ berisso @ |
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675 |
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