Magnetism and structure of Cu2O1+x and 3d-doped TiO2−x nanopowders

Yermakov, A. Ye.; Уймин, М. А.; Мысик, А. А.; Выходец, В. Б.; Куренных, Т. Е.; Sokolov, V. I.; Гавико, В. С.; Schegoleva, N.N.; Gruzdev, N. B.

doi:10.1016/j.jmmm.2006.10.780

Cited by 19 publications

(15 citation statements)

References 7 publications

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“…The latter should not be excluded, since the ferro magnetic state in Cu [15] and Cu 2 O [16] NPd was found experimentally at room temperature and grounded theoretically [17]. However, taking into The magnetization of the charge from the micron CeO 2 powder was 5 × 10 -4 emu/g (Fig.…”

Section: Discussion Of Nanopowders Morphology and Structurementioning

confidence: 91%

Production and studies of properties of nanopowders on the basis of CeO2

Il’ves

Sokovnin

2012

Nanotechnol Russia

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Nanopowders (NPds) of pure CeO 2 of a specific surface area up to 210 m 2 /g and those doped with copper, carbon, and iron (≤1 wt % of dopant) of a specific surface area in the range 130-160 m 2 /g have been produced by evaporation with a pulsed electron beam. According to the X ray phase analysis data, no sec ondary phases (aside from the cubic CeO 2 phase) were found in the produced NPds. All the powders con tained fine and coarse crystalline fractions differing in the size of their coherent scattering region (CSR) and in their amorphous component. The degree of crystallinity of the powders was not above 22%. The powders have a fractal structure and consist of agglomerates of sizes from dozens to hundreds of nanometers formed by crystalline nanoparticles (NPts) 3-5 nm in size with a very narrow particle size distribution. NPds have a high structural defectiveness degree, which was reflected in their magnetic properties. The room ferromag netism was established in NPds of pure CeO 2 -x and those doped with nonmagnetic elements (carbon and copper): here the ferromagnetic state in the CeO 2 C system was established for the first time, whereas the magnetic moment on the carbon atom was 35 fold lower than the theoretical estimation. The ferromagnetic contribution to CeO 2 NPd increases with a decrease in the NPt size and reaches 0.1 emu/g in CeO 2 Fe NPd (x Fe = 0.54 wt %). It has been established that there is no direct dependence between magnetization and the content of iron ions in the CeO 2 Fe based NPds.

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Section: Discussion Of Nanopowders Morphology and Structurementioning

confidence: 91%

Production and studies of properties of nanopowders on the basis of CeO2

Il’ves

Sokovnin

2012

Nanotechnol Russia

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“…It has been established experimentally [33][34][35] and theoretically 7,8,14 that the dominant point defects in cuprous oxide under varying oxygen conditions are both neutral and singly negatively charged copper vacancies. As reported, both the electronic and magnetic properties of Cu 2 O is sensitively influenced by its ͑sub-͒stoichiometry and growth conditions, [31][32][33][34] thus reinforcing the need to investigate how deviation from its natural stoichiometry ͑i.e., in the presence of native defects͒ will affect these properties ͑and thus functionality͒ in Cu 2 O. Using the projector-augmented-wave ͑PAW͒ method and the generalized gradient approximation ͑GGA͒, Nolan and Elliott 7 performed density-functional theory ͑DFT͒ calculations, investigating the p-type conduction mechanism in Cu 2 O, and concluded that the p-type semiconducting properties seen in Cu 2 O are attributed to small concentrations of Cu vacancies.…”

Section: Introductionmentioning

confidence: 91%

“…31,32 Interestingly, it has also been shown recently that, at room temperature, nanoparticulates ͑7-30 nm͒ ͑Ref. 30͒ of otherwise nonmagnetic oxides, e.g., SnO 2 , Al 2 O 3 , or even CeO 2 , are ferromagnetic as well as thin oxide films of similar ceramic oxides.…”

Section: Environment-dependent Nanomorphologymentioning

confidence: 99%

“…Thus for the bulk material, despite having such low formation energies ͑i.e., should exist in high concentrations under growth conditions͒, these copper defects are not responsible for the experimentally observed magnetism. 31,32 On the other hand, the oxygen interstitial defects O i͑oct͒ and O i͑tet͒ are found to be magnetic. We first examine the magnetic properties for the neutral defects before proceeding to the charged defects.…”

Section: Magnetic Structure Of Low-energy Defectsmentioning

confidence: 99%

“…[25][26][27][28][29][30] This has prompted many researchers to ͑re-͒investigate the fundamental properties of such semiconducting oxides, focusing largely on their deviation from natural stoichiometry and the role of native defects. In relation to Cu 2 O, Yermakov and co-workers 31,32 have found that nanocrystalline powder samples of nonstoichiometric Cu 2 O ͑i.e., Cu 2−␦ O͒ exhibit magnetic hysteresis properties of up to 400 K, suggesting ferromagnetic behavior. These nanoparticles are of 10-100 nm in size and their magnetic properties are reported to be highly dependent on the oxygen concentration during their formation.…”

Section: Introductionmentioning

confidence: 99%

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Native defect-induced multifarious magnetism in nonstoichiometric cuprous oxide: First-principles study of bulk and surface properties ofCu2−δO

et al. 2009

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Native defects in cuprous oxide Cu 2 O are investigated by using first-principles calculations based on density-functional theory. Considering the formation of copper and oxygen vacancies, antisites and interstitials, and a copper split-vacancy complex defect, we analyze the electronic structure and calculate their respective formation energies as a function of the change in Fermi level under both copper-rich and oxygen-rich conditions. We find that, under both growth conditions, the defect with the lowest formation energy is the simple copper vacancy, followed by the copper split-vacancy complex. Both low-energy copper defects produce hole states at the top of the valence band, largely accounting for the p-type conductivity in this material. In spite of the creation of dangling bonds at the nearest-neighbor O atoms, these copper defects are found to be spin neutral. Under oxygen-rich conditions, oxygen interstitials have low formation energies and are found to exhibit a ferromagnetic ordering with a total magnetic moment of 1.38 B and 1.36 B at the octahedral and tetrahedral sites, respectively. Considering the possibility of native defect formation at the surface of this material, we investigate the relative stability of both low-and high-index copper-oxide surfaces by comparing their surface free energies as a function of the change in oxygen chemical potential. Using the technique of ab initio atomistic thermodynamics, we then correlate the dependence of the calculated Gibbs free-surface energy as a function of oxygen pressure and temperature via the oxygen chemical potential. We identify two lowenergy surface structures, namely, Cu 2 O͑110͒ : CuO and Cu 2 O͑111͒-Cu CUS , with the former marginally more stable for oxygen-rich conditions and the latter more stable for oxygen-lean ͑or copper-rich͒ conditions. Cu 2 O͑110͒ : CuO is calculated to be nonmagnetic and Cu 2 O͑111͒-Cu CUS is calculated to be a ferromagnetic ordering, with a total magnetic moment of 0.91 B per defect. With the results for both bulk and surface native defects, we find that under oxygen-lean conditions, a ferromagnetic behavior could be attributed mainly to copper vacancy formation in the ͑111͒ surface of Cu 2 O while under oxygen-rich conditions, low-energy bulk oxygen interstitial defects induce a ferromagnetic character in the same material. This highlights the complementary role of bulk and surface native magnetic defects under different pressure and temperature conditions, especially at the nanoparticle scale where surface properties dominate.

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Preparation, characterization and nonlinear absorption studies of cuprous oxide nanoclusters, micro-cubes and micro-particles

Sekhar

Rao

2012

J Nanopart Res

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Magnetism and structure of Cu2O1+x and 3d-doped TiO2−x nanopowders

Cited by 19 publications

References 7 publications

Production and studies of properties of nanopowders on the basis of CeO2

Production and studies of properties of nanopowders on the basis of CeO2

Native defect-induced multifarious magnetism in nonstoichiometric cuprous oxide: First-principles study of bulk and surface properties ofCu2−δO

Preparation, characterization and nonlinear absorption studies of cuprous oxide nanoclusters, micro-cubes and micro-particles

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