Supporting Information: Unexpected chain of redox events in co-based Prussian blue analogues

Comprehensive characterizing information about the series of materials; crystal, composition, and hyperfine parameters of the 57Fe Mössbauer spectra of samples K2−δMn1–xCox[Fe(CN)6]; SAED and TGA patterns, HAADF-STEM images, ATR–FTIR, 57Fe Mössbauer spectra, and electrochemical galvanostatic profiles of the mentioned series of samples; calculated fit of XAS experiments; and plots of KCMF50 and KCF operando SXRD in a 10–54° 2Θ range (λ = 1.0332 Å).Peer reviewe

The stabilization of the highest oxidation states of transition metals under oxygen pressures: TlNiO3, a new Ni(III) perovskite - comparison of the electronic properties with those of TNiO3 (T = rare earth and Y)

The crystal structure and the magnetic properties of TlNiO3 have been characterized and compared with those of TNiO3 (T = rare earth and Y). The electronic structure of Ni(III) has been investigated by Mössbauer spectroscopy. Through these analyses, the effects of the A-site ion on structural distortion, magnetic behaviour and electronic structure of Ni(III) in a perovskite have been discussed

The phyllosiloxides : new class of layered oxides derived from natural phyllosilicates

New class of layered oxides, phyllosiloxides, was expanded to three new compositions: KMg2Fe3+Si4O12, rm{KFe}ˆ{2+}_{2}rm{AlSi}_{4}rm{O}_{12}, and rm{KFe}ˆ{2+}rm{Fe}ˆ{3+}_{3}rm{Si}_{3}rm{O}_{12}. The sol-gel route was adopted to prepare a precursor and the polycrystalline samples were obtained by solvothermal treatments at 750 °C/160 MPa using 2-methoxy ethanol as solvent. The three powder X-ray diffraction patterns were successfully indexed by 1 M polytype of mica. Platelet morphologies of these samples were observed through the images of scanning electron microscopy

High oxygen pressures and the improvement of the Mn+ -- O chemical bond through the stabilization of the highest oxidation states (n+)

International audienceAn evolution of local structure of Ni and chemical bonding, Ni(III)-O in perovskite lattice with strongly distorted structure is investigated with 57Fe Mössbauer spectroscopy. The Mössbauer spectra for 57Fe-doped TlNiO3 were resolved to two quadrupole doublets with different isomer shifts, which underlines a partial charge disproportionation phenomenon: 2Fe3+ -> Fe3+alpha +Fe3-alpha. This result supports the existence of two different crystallographic sites for Ni in the distorted perovskite lattice

Synthesis, structure, and magnetic and dielectric properties of magnetoelectric BaDyFeO4 ferrite

BaDyFeO4 was prepared by a conventional solid-state method in air at 1573 K. It crystallizes in space group Pnma (No. 62) with a = 13.16861(1) angstrom, b = 5.70950(1) angstrom, and c = 10.26783(1) angstrom, and it is isostructural with BaYFe0 4 . Three magnetic transitions were found in BaDyFeO4 at T-N3 = 9 K, T-N2 = 23 K, and T-N1 =47 K in zero magnetic field in comparison with two magnetic transitions observed in BaYFeO4. Magnetic-field-induced transitions were also detected in BaDyFeO4 at 18 and 28 kOe (at T= 1.8 K). Frequency-dependent broad dielectric peaks were observed in BaDyFeO4 spanning between T-N2 and T-N and centred at 35 K - this temperature does not coincide with any T-N. No dielectric anomalies were found at T-N1 and T-N3, while very weak frequency-independent dielectric anomalies were detected at T-N2. Positive and negative magnetodielectric effects were measured in BaDyFeO4 (within a range of -0.8 and + 0.4% up to 90 kOe) reflecting magnetic-field dependence of dielectric constant. Pyroelectric current measurements did not detect any ferroelectricity in BaDyFeO4 under measurement conditions used. No dielectric anomalies and no magnetodielectric effects were found in BaYFeO4. (C) 2019 Elsevier B.V. All rights reserved

Ferromagnetic Order, Strong Magnetocrystalline Anisotropy, and Magnetocaloric Effect in the Layered Telluride Fe_3−δGeTe₂

The ternary transition-metal compound Fe_3−δGeTe₂ is formed for 0 < δ < 0.3. X-ray diffraction and Mössbauer spectroscopy reveal its layered crystal structure with occasional Fe vacancies in the Fe2 site, whereas no Fe atoms occupy the interlayer space, so that only van der Waals interactions exist between adjacent layers. We explore magnetic behavior and ensuing functional properties of Fe_2.9GeTe₂ via neutron diffraction, thermodynamic and transport measurements, Mössbauer spectroscopy, and electronic structure calculations. Below <i>T</i>_C = 225 K, Fe_2.9GeTe₂ is ferromagnetically ordered with the magnetic moments of 1.95(5) and 1.56(4) μ_B at <i>T</i> = 1.5 K, both directed along <i>c</i>, which is the magnetic easy axis. Electronic structure calculations confirm this magnetic structure and reveal a remarkably high easy-axis anisotropy of 4.2 meV/f.u. Mössbauer spectra reveal the magnetic ordering too, although a drastic influence of Fe vacancies on quadrupolar splittings and local magnetic fields has been observed. A moderate magnetocaloric effect with the magnetic entropy change upon the ferromagnetic ordering transition, −Δ<i>S</i> ∼ 1.1 J·kg^–1·K^–1 at 5 T, is found

Direct evidence of non-Zhang-Rice Cu3+ centers in La2Li0.5Cu0.5O4

International audienceA well-isolated Zhang-Rice (ZR) singlet as a ground state of the Cu3+ center in hole-doped cuprates is a leading paradigm in modern theories of high-temperature superconductivity. However, a dramatic temperature evolution of the 6,7Li NMR signal in La2Li0.5Cu0.5O4, a system with a regular lattice of well-isolated Cu3+ centers, reveals significant magnetic fluctuations and suggests a quasidegeneracy to be a generic property of their ground state at variance with the simple ZR model. We argue for a competition of the ZR state with nearby states formed by a "doped" hole occupying purely oxygen nonbonding a2g(π) and eu(π) orbitals rather than a conventional b1g(dx2−y2) Cu 3d-O 2p hybrid. The temperature variation of the 6,7Li NMR line shape and spin-lattice relaxation rate point to a gradual slowing down of some magnetic order parameter's fluctuations without distinct signatures of a phase transition down to T=2 K. This behavior agrees with a stripelike ferrodistortive fluctuating Ammm order in a two-dimensional structure of the (CuLi)O2 planes accompanied by unconventional oxygen orbital antiferromagnetic fluctuations

Orbital ordering in NdNiO3 and SmNiO3 investigated by Mössbauer spectroscopy

A Mössbauer study of 57Fe doped NiIII perovskites, NdNi0.98Fe0.02O3 and SmNi0.98Fe0.02O3, in the magnetic ordering domain (T≪TN) has revealed that the Fe probes occupy two types of sites, i.e., Fe(1) and Fe(2), showing very different values of the magnetic hyperfine fields (H1≈430-450kOe,H2≈15-22kOe). The close values of the isomer shift (δ) and the second-order quadrupole perturbation parameter (ɛ) in the subspectra, for both Fe sites, have underlined that all the Fe sites are crystallographically equivalent. In the light of orbital ordering model suggested by the neutron diffraction studies, the partial substitution of NiIII (t2g6eg1) by Fe3+ (t2g3eg2) may induce significant topological frustration of Fe3+ spins in surroundings of NiIII orbitals, leading to two different magnetic environments around Fe below TN. Additionally, the Mössbauer spectra at 300 K (>TN) indicate that all the available sites for probe atoms are crystallographically equivalent in the insulating SmNi0.98Fe0.02O3 as well as in the metallic NdNi0.98Fe0.02O3. The present result may be an evidence of the important role of the orbital ordering in determining the electronic properties of the NiIII perovskites containing large rare earth