Structural, magnetic and magnetoelectric studies of BaTiO3:Co nanocomposite films formed by ion-beam methods

Thin-film samples of ferroelectric barium titanate (BaTiO3) with cobalt nanoparticles were obtained by using either ion implantation or ion beam sputtering deposition (IBSD) techniques. The samples were characterized using X-ray diffraction, transmission electron microscopy, magnetometry and ferromagnetic resonance to investigate the efficiency of above ion-beam methods in the synthesis of magnetoelectric nanocomposite materials. Our structural studies show that high-fluence implantation with Co+ ions results in the formation of cobalt nanoparticles with mean size of 5 nm in thin surface layer of monocrystalline plate of BaTiO3. On the other hand, larger nanoparticles of cobalt with sizes from 5 up to 40 nm are formed in polycrystalline BaTiO3 matrix only after high-temperature annealing of BaTiO3:Co composite film prepared by IBSD method. Both types of thin-film nanocomposite samples have similar magnetic hysteresis curves in the sample plane. However Co-implanted BaTiO3 reveals strong uniaxial magnetic anisotropy for out-of-plane orientation, while BaTiO3:Co nanocomposite film demonstrates almost isotropic magnetic response. Strong magnetoelectric effect are observed in Co-implanted BaTiO3, and no magnetoelectric coupling are detected in BaTiO3:Co nanocomposite film formed by IBSD with subsequent high-temperature annealing. © 2014 Elsevier B.V. All rights reserved

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

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

Structure of the local environment and hyperfine interactions of ⁵⁷Fe probe atoms in DyNiO₃ nickelate

The local structure of DyNiO3 nickelate at both sides of the insulator (T T im) phase transition was studied by probe 57Fe Mössbauer spectroscopy. The character of change in the hyperfine parameters of probe iron atoms specifically near the phase-transition temperature (T ≈ T im) was analyzed

Electronic state of 57Fe used as Mössbauer probe in the perovskites LaMO3 (M=Ni and Cu)

For the first time a comparative study of rhombohedral LaNiO3 and LaCuO3 oxides, using 57Fe Mössbauer probe spectroscopy (1% atomic rate), has been carried out. In spite of the fact that both oxides are characterized by similar crystal structure and metallic properties, the behavior of 57Fe probe atoms in such lattices appears essentially different. In the case of LaNi0.99Fe0.01O3, the observed isomer shift (δ) value corresponds to Fe3+ (3d5) cations in high-spin state located in an oxygen octahedral surrounding. In contrast, for the LaCu0.99Fe0.01O3, the obtained δ value is comparable to that characterizing the formally tetravalent high-spin Fe4+(3d4) cations in octahedral coordination within Fe(IV) perovskite-like ferrates. To explain such a difference, an approach based on the qualitative energy diagrams analysis and the calculations within the cluster configuration interaction method have been developed. It was shown that in the case of LaNi0.99Fe0.01O3, electronic state of nickel is dominated by the d7 configuration corresponding to the formal ionic “Ni3+–O2−” state. On the other hand, in the case of LaCu0.99Fe0.01O3 a large amount of charge is transferred via Cu–O bonds from the O:2p bands to the Cu:3d orbitals and the ground state is dominated by the d9L configuration (“Cu2+−O” state)..

Local Environment and Electronic Structure in K2NiF4-type La2Li0.50Cu0.50O4 Doped by 57Fe

The 57Fe M¨ossbauer spectrum of the oxide La2Li0.50Cu0.50O4 doped with 57Fe (1 at.-%) underlines at 300 K the presence of three different components: two corresponding to the substitution of 57Fe probe atoms for respectively “Cu3+” [Fe(1)] and Li+ [Fe(3)] and the third [Fe(2)] attributed to 57Fe associated with oxygen vacancies. A decrease of the temperature down to 77 K does not lead to essential changes of the M¨ossbauer parameters corresponding to the Fe(1) and Fe(2) sub-spectra. On the contrary, a drastic change occurs in the Fe(3) sub-spectrum which has been interpreted by a displacement of the charge-transfer equilibrium Fe4+(3) + O2− →Fe3+(3) + O(L) at the Li+ sites