Evidence for a strong spin-phonon interaction in cupric oxide

Chen, X. K.; Irwin, J. C.; Franck, J. P.

doi:10.1103/physrevb.52.r13130

Cited by 127 publications

(104 citation statements)

References 31 publications

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“…Spin-phonon interactions have been found to have a strong effect on Raman scattering in a number of systems, including cupric oxide (29) and the copper-ruthenium oxide RuSr 2 GdCu 2 O 8 (30). The general character of the effect of spin-phonon interaction on the Raman spectra in these materials is consistent with the observations for hcp iron: broad, low amplitude, satellite peaks appear when the sample is below the Curie or Néel temperature.…”

supporting

confidence: 73%

Magnetism in dense hexagonal iron

Steinle‐Neumann

Stixrude

Cohen

2003

Proc. Natl. Acad. Sci. U.S.A.

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The magnetic state of hexagonal close-packed iron has been the subject of debate for more than three decades. Although Mö ssbauer measurements find no evidence of the hyperfine splitting that can signal the presence of magnetic moments, density functional theory predicts an antiferromagnetic (afm) ground state. This discrepancy between theory and experiment is now particularly important because of recent experimental findings of anomalous splitting in the Raman spectra and the presence of superconductivity in hexagonal close-packed iron, which may be caused by magnetic correlations. Here, we report results from first principles calculations on the previously predicted theoretical collinear afm ground state that strongly support the presence of afm correlations in hexagonal close-packed iron. We show that anomalous splitting of the Raman mode can be explained by spinphonon interactions. Moreover, we find that the calculated hyperfine field is very weak and would lead to hyperfine splitting below the resolution of Mö ssbauer experiments. P hysical properties of iron are of great importance to many fields in the sciences, as iron is one of the most abundant and stable elements in the universe and the very basis for the steel industry. Hexagonal close-packed (hcp) iron, the form stable at high pressure, plays a central role in geophysics, as the Earth's inner core is thought to be primarily composed of this phase (1, 2), and in our understanding of impact and explosive phenomena in iron and steel (3). The magnetic state of iron has a major influence on the physics of iron and iron alloys, including the relative stability of the iron polymorphs (4, 5). The magnetic structure of the hcp phase has been the subject of a scientific debate for three decades (6), leading to contradictory results from experiments and theory. Although experiments are interpreted to show the absence of magnetism in hcp iron (6-10), computations based on density functional theory find an antiferromagnetic (afm) ground state stable to Ϸ50 GPa (11), similar to magnetism in the double hcp phase (5). The possible presence of magnetism in hcp iron as further substantiated in this article has important implications. In geophysics many experiments are carried out on potentially magnetic hcp iron and are then extrapolated to pressures of Earth's core, into the nonmagnetic region of the hcp stability field at high pressure, and may consequently not be valid. The possible presence of magnetism in hcp iron also plays an important role in the discussion of the recently observed superconductivity of hcp iron (12, 13): Magnetic correlations in hcp iron appear to be necessary to explain the observed pressure dependence of its superconductivity (14-16).The two lower-pressure polymorphs of iron are both magnetic. The phase stable around ambient conditions, body-centered cubic (bcc), owes its stability entirely to the presence of ferromagnetism (4). Heating above the Curie temperature causes the spins to disorder and the net magnetization to vanish, but the ind...

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supporting

confidence: 73%

Magnetism in dense hexagonal iron

Steinle‐Neumann

Stixrude

Cohen

2003

Proc. Natl. Acad. Sci. U.S.A.

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“…However, the use of more sophisticated functionals 52,60,[90][91][92][93] allows for the reproduction of the triclinic structure and good agreement with experiments on structural and vibrational data [94][95][96][97] (see Table 2). …”

Section: Cuo Bulk Propertiesmentioning

confidence: 99%

Atomistic details of oxide surfaces and surface oxidation: the example of copper and its oxides

Gattinoni

Michaelides

2015

Surface Science Reports

279

258

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The oxidation and corrosion of metals are fundamental problems in materials science and technology that have been studied using a large variety of experimental and computational techniques. Here we review some of the recent studies that have led to significant advances in our atomic-level understanding of copper oxide, one of the most studied and better understood metal oxides. We show that a good atomistic understanding of the physical characteristics of cuprous (Cu 2 O) and cupric (CuO) oxide and of some key processes of their formation has been obtained. Indeed, the growth of the oxide has been proven to be epitaxial with the surface and to proceed, in most cases, through the formation of oxide nano-islands which, with continuous oxygen exposure, grow and eventually coalesce. We also show how electronic structure calculations have become increasingly useful in helping to characterise the structures and energetics of various Cu oxide surfaces. However a number of challenges remain. For example, it is not clear under which conditions the oxidation of copper in air at room temperature (known as native oxidation) leads to the formation of a cuprous oxide film only, or also of a cupric overlayer. Moreover, the atomistic details of the nucleation of the oxide islands are still unknown. We close our review with a perspective on future work and discuss how recent advances in experimental techniques, bringing greater temporal and spatial resolution, along with improvements in the accuracy, realism and timescales achievable with computational approaches make it possible for these questions to be answered in the near future.

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“…S1). Estimates were also made of the size of the CuO nanoparticles using the Scherrer formula using the CuO (111) diffraction peak [44]. Assuming a homogeneous strain across the crystallites, the size of the grains can be estimated from the full-width half-maximum (FWHM) values of the diffraction peaks.…”

Section: Pyrolysis Of the Precursorsmentioning

confidence: 99%