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844 results on '"Baggio-Saitovitch, E."'

104. Aggregates of iron in ytterbium films

Author

Herrera, W. T., primary, Rojas-Ayala, C., additional, Dinóla, I. S., additional, Passamani, E. C., additional, Kraken, M., additional, Engelke, J., additional, Baggio-Saitovitch, E., additional, and Litterst, F. J., additional

Published
2011
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117. Dimensional crossover in Cr-doped Co3BO5

Author

Mariano, D. L., primary, Heringer, M. A. V., additional, Freitas, D. C., additional, Baggio-Saitovitch, E., additional, Continentino, M. A., additional, Passamani, E. C., additional, and Sanchez, D. R., additional

Published
2020
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123. The zero-field-cooled exchange bias effect in phase-segregated La$_{2-x}$A$_{x}$CoMnO$_{6-��}$ (A = Ba, Ca, Sr; x = 0, 0.5)

Author

Coutrim, L. T., Rigitano, D., Macchiutti, C., Mori, T. J. A., Lora-Serrano, R., Granado, E., Sadrollahi, E., Litterst, F. J., Fontes, M. B., Baggio-Saitovitch, E., Bittar, E. M., and Bufai��al, L.

Subjects
Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences
Abstract

In the zero-field-cooled exchange bias (ZEB) effect the unidirectional magnetic anisotropy is set at low temperatures even when the system is cooled in the absence of external magnetic field. La$_{1.5}$Sr$_{0.5}$CoMnO$_{6}$ stands out as presenting the largest ZEB reported so far, while for La$_{1.5}$Ca$_{0.5}$CoMnO$_{6}$ the exchange bias field ($H_{EB}$) is one order of magnitude smaller. Here we show that La$_{1.5}$Ba$_{0.5}$CoMnO$_{6}$ also exhibits a pronounced shift of its magnetic hysteresis loop, with intermediate $H_{EB}$ value in respect to Ca- and Sr-doped samples. In order to figure out the microscopic mechanisms responsible for this phenomena, these compounds were investigated by means of synchrotron X-ray powder diffraction, Raman spectroscopy, muon spin rotation and relaxation, AC and DC magnetization, X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). The parent compound La$_{2}$CoMnO$_{6}$ was also studied for comparison, as a reference of a non-ZEB material. Our results show that the Ba-, Ca- and Sr-doped samples present a small amount of phase segregation, and that the ZEB effect is strongly correlated to the system's structure. We also observed that mixed valence states Co$^{2+}$/Co$^{3+}$ and Mn$^{4+}$/Mn$^{3+}$ are already present at the La$_{2}$CoMnO$_{6}$ parent compound, and that Ba$^{2+}$/Ca$^{2+}$/Sr$^{2+}$ partial substitution at La$^{3+}$ site leads to a large increase of Co average valence, with a subtle augmentation of Mn formal valence. Estimates of the Co and Mn valences from the $L$-edge XAS indicate the presence of oxygen vacancies in all samples (0.05$\leq ��\leq$0.1). Our XMCD results show a great decrease of Co moment for the doped compounds, and indicate that the shift of the hysteresis curves for these samples is related to uncompensated antiferromagnetic coupling between Co and Mn., 13 pages, 9 figures + supplementary material

Published
2019
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124. Pressure effects on the structural and superconducting transitions in $\mathrm{La_{3}Co_{4}Sn_{13}}$

Author

Mendonça-Ferreira, L., Carneiro, F. B., Fontes, M. B., Baggio-Saitovitch, E., Veiga, Larissa, Mardegan, J. R. L., Strempfer, J., Piva, M. M., Pagliuso, P. G., Dos Reis, R. D., and Bittar, E. M.

Subjects
Condensed Matter::Materials Science, Condensed Matter::Superconductivity, ddc:540, Condensed Matter::Strongly Correlated Electrons
Abstract

Journal of alloys and compounds 773, 34 - 39 (2019). doi:10.1016/j.jallcom.2018.09.236, La$_3$Co$_4$Sn$_{13}$ is a superconducting material with transition temperature at $T_c = 2.70.$ K, which presents a superlattice structural transition at $T^* \simeq 150$ K, a common feature for this class of compounds. However, for this material, it is not clear that at $T^*$ the lattice distortions arise from a charge density wave (CDW) or from a distinct microscopic origin. Interestingly, it has been suggested in isostructural non-magnetic intermetallic compounds that $T^*$ can be suppressed to zero temperature, by combining chemical and external pressure, and a quantum critical point is argued to be observed near these critical doping/pressure. Our study shows that application of pressure on single-crystalline La$_3$Co$_4$Sn$_{13}$ enhances $T_c$ and decreases $T^*$. We observe thermal hysteresis loops for cooling/heating cycles around $T^*$ for $P \gtrsim 0.6$ GPa, in electrical resistivity measurements, which are not seen in x-ray diffraction data. The hysteresis in electrical measurements may be due to the pinning of the CDW phase to impurities/defects, while the superlattice structural transition maintains its ambient pressure second-order transition nature under pressure. From our experiments we estimate that $T^*$ vanishes at around 5.5 GPa, though no quantum critical behavior is observed up to 2.53 GPa., Published by ScienceDirect, Amsterdam [u.a.]

Published
2019
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134. Preface

Author

Mercader, R. C., Gancedo, J. R., Prieto, A. Cabral, and Baggio-Saitovitch, E.

Published
2005

147. Heavy fermion Ce3Co4Sn13 compound under pressure.

Author

Collave, J. R., Borges, H. A., Ramos, S. M., Hering, E. N., Fontes, M. B., Baggio-Saitovitch, E., Mendonça-Ferreira, L., Bittar, E. M., and Pagliuso, P. G.

Subjects
FERMIONS, MAGNETORESISTANCE, ELECTRIC resistance, ELECTRICAL resistivity, FORCE density
Abstract

The non-magnetic heavy fermion compound Ce3Co4Sn13 was studied under pressure. We report single crystalline measurements of electrical resistivity as a function of temperature ρ(T) under pressure. Some characteristic features related to a structural transition (TS), crystalline field effects (TCEF), and a low temperature maximum (Tmax), possibly connected simultaneously to the onset of Kondo lattice coherence and short range magnetic correlations, were identified in the ρ(T) data. A pressure-temperature phase diagram with TS and Tmax was constructed by mapping these features. Like for most Ce-based heavy fermion compounds, Tmax moves to higher temperatures with pressure, indicating that it is related to the Kondo energy scale, due to the increase of hybridization induced by pressure. On the other hand, TS, associated to a superlattice distortion and probably combined with a charge density wave transition, decreases as a function of pressure. However, differently from the Sr3-xCaxIr4Sn13 system, where a superlattice quantum phase transition is observed [L. E. Klintberg et al., Phys. Rev. Lett. 109, 237 008 (2012)], in Ce3Co4Sn13 TS~154 K, at ambient pressure (P = 0), seems to stabilize at around 143K for P ⩾ 19 kilobars. We also investigated ρ(T) in external magnetic fields, at P = 0. Negative magnetoresistance and increase of Tmax are observed, suggesting suppression of low temperature short range magnetic correlations. [ABSTRACT FROM AUTHOR]

Published
2015
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