16 research outputs found
Spin–lattice and electron–phonon coupling in 3d/5d hybrid Sr3NiIrO6
Research at the University of Tennessee, Rutgers University, and University of Minnesota is supported by the National Science Foundation DMREF program (DMR-1629079, DMR-1629059, and DMR-1629260, respectively). The crystal growth was partially supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (No. 2016K1A4A4A01922028). We also appreciate funding from the U.S. Department of Energy, Basic Energy Sciences, contract DE-FG02-01ER45885 (Tennessee), “Science at 100 Tesla” (LANL), and “Topological phases of quantum matter and decoherence” (LANL). The NHMFL facility is supported by the U.S. National Science Foundation through Cooperative Grant DMR-1644779, the State of Florida, and the U.S. Department of Energy.While 3d-containing materials display strong electron correlations, narrow band widths, and robust magnetism, 5d systems are recognized for strong spin–orbit coupling, increased hybridization, and more diffuse orbitals. Combining these properties leads to novel behavior. Sr3NiIrO6, for example, displays complex magnetism and ultra-high coercive fields—up to an incredible 55 T. Here, we combine infrared and optical spectroscopies with high-field magnetization and first-principles calculations to explore the fundamental excitations of the lattice and related coupling processes including spin–lattice and electron–phonon mechanisms. Magneto-infrared spectroscopy reveals spin–lattice coupling of three phonons that modulate the Ir environment to reduce the energy required to modify the spin arrangement. While these modes primarily affect exchange within the chains, analysis also uncovers important inter-chain motion. This provides a mechanism by which inter-chain interactions can occur in the developing model for ultra-high coercivity. At the same time, analysis of the on-site Ir4+ excitations reveals vibronic coupling and extremely large crystal field parameters that lead to a t2g-derived low-spin state for Ir. These findings highlight the spin–charge–lattice entanglement in Sr3NiIrO6 and suggest that similar interactions may take place in other 3d/5d hybrids.Publisher PDFPeer reviewe
Estruturação dos objetivos de aprendizagem para ambientes de educação on-line
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência da Computação.O objetivo deste trabalho é prover o processo e a avaliação funcional dos componentes que compõem um ambiente de e-aprendizagem baseado em Objetos de aprendizagem, apresentando as definições, propriedades e aplicações dos Objetos de aprendizagem, que se referem à criação e reutilização dos objetos para desenvolver ambientes de aprendizagem. Os padrões utilizados para desenvolvimento de conteúdos estruturados para ambientes de aprendizagem para Web também serão descritos. Também é abordado o potencial da Web semântica, a qual transforma a Web em um meio em que a informação é interpretada, trocada e processada. Apresentar como a linguagem XML e a orientação a objeto se relacionam com os Objetos de aprendizagem é outro tópico abordado. O trabalho inclui, ainda, um protótipo para um ambiente de aprendizagem online utilizando os objetos de aprendizagem
Charge and Bonding in CuGeO<sub>3</sub> Nanorods
We
combine infrared and Raman spectroscopies to investigate finite
length scale effects in CuGeO<sub>3</sub> nanorods. The infrared-active
phonons display remarkably strong size dependence whereas the Raman-active
features are, by comparison, nearly rigid. A splitting analysis of
the Davydov pairs reveals complex changes in chemical bonding with
rod length and temperature. Near the spin-Peierls transition, stronger
intralayer bonding in the smallest rods indicates a more rigid lattice
which helps to suppress the spin-Peierls transition. Taken together,
these findings advance the understanding of size effects and collective
phase transitions in low-dimensional oxides
Local Lattice Distortions in Mn[N(CN)<sub>2</sub>]<sub>2</sub> under Pressure
We combined synchrotron-based infrared
spectroscopy, Raman scattering, and diamond anvil cell techniques
with complementary lattice dynamics calculations to reveal local lattice
distortions in MnÂ[NÂ(CN)<sub>2</sub>]<sub>2</sub> under compression.
Strikingly, we found a series of transitions involving octahedral
counter-rotations, changes in the local Mn environment, and deformations
of the superexchange pathway. In addition to reinforcing magnetic
property trends, these pressure-induced local lattice distortions
may provide an avenue for the development of new functionalities
Spin–lattice and electron–phonon coupling in 3<i>d</i>/5<i>d</i> hybrid Sr<sub>3</sub>NiIrO<sub>6</sub>
While 3d-containing materials display strong electron correlations, narrow band widths, and robust magnetism, 5d systems are recognized for strong spin–orbit coupling, increased hybridization, and more diffuse orbitals. Combining these properties leads to novel behavior. Sr3NiIrO6, for example, displays complex magnetism and ultra-high coercive fields—up to an incredible 55 T. Here, we combine infrared and optical spectroscopies with high-field magnetization and first-principles calculations to explore the fundamental excitations of the lattice and related coupling processes including spin–lattice and electron–phonon mechanisms. Magneto-infrared spectroscopy reveals spin–lattice coupling of three phonons that modulate the Ir environment to reduce the energy required to modify the spin arrangement. While these modes primarily affect exchange within the chains, analysis also uncovers important inter-chain motion. This provides a mechanism by which inter-chain interactions can occur in the developing model for ultra-high coercivity. At the same time, analysis of the on-site Ir4+ excitations reveals vibronic coupling and extremely large crystal field parameters that lead to a t2g-derived low-spin state for Ir. These findings highlight the spin–charge–lattice entanglement in Sr3NiIrO6 and suggest that similar interactions may take place in other 3d/5d hybrids