Bogdan Dabrowski

Northern Illinois University · Department of Physics

Specific heat studies of the Sr$_{1-x}$Ba$_x$Mn$_{1-y}$Ti$_y$O$_3$ polycrystalline samples performed by the relaxation and DSC methods over the temperature range 2 - 450 K are reported. Anomalies accompanying the antiferromagnetic-paramagnetic and ferroelectric-paraelectric phase transitions were measured and analyzed. The system studied is a promi...

In this work, we investigated the critical currents and pinning mechanisms in single crystals of the high-temperature superconductor Y123 with Mo substituted into CuO chains. The single crystals were annealed in oxygen at low (130–140 atm) and high (255 atm) pressure, which significantly influenced the observed properties. Magnetic hysteresis loops...

La1.5Ba1.5Cu3O7±δ (LBCu) complex oxide is evaluated as a Co-free candidate air electrode material for reversible Solid Oxide Cells (rSOC). LBCu is structurally and thermomechanically compatible with La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte, maintains the layered (tripled along the c-axis) perovskite-related crystal structure at high temperatures...

We have previously shown for powders that Mo substitution into the CuO chains of YBa2Cu3O7 can create effective pinning centres which significantly increase the critical current density (jc) in 7 T field by a factor of 4 and 10 at 50 and 60 K, respectively (Rogacki et al., 2006) [1]. The present work reports on the influence of the Mo substitution...

It is documented that the mean radius r¯ of rare-earth cations occupying Y1-xRx sublattice in Y1-xRxMnO3+δ hexagonal oxides plays a decisive role in terms of thermodynamics and kinetics of reactivity of the materials with oxygen, and consequently, influences strongly the oxygen storage performance in thermal swing processes conducted in oxygen and...

Hexagonal Y1−xRxMnO3+δ (R: other than Y rare earth elements) oxides have been recently introduced as promising oxygen storage materials that can be utilized in the temperature swing processes for the oxygen separation and air enrichment. In the present work, the average and local structures of Tb- and Ce-substituted Y0.7Tb0.15Ce0.15MnO3+δ and Y0.6T...

Muliferroic materials are characterized by two or more primary ferroic orders: ferroelectric, ferromagnetic and ferroelastic. In multiferroics the coupling occurs between the magnetic (ferromagnetic or antiferromagnetic) and electric (ferroelectric) subsystems. This enables control of the dielectric polarization P by a magnetic field H and the mani...

High Cu content perovskite-type LaNi1-xCuxO3-δ oxides are evaluated as alternative air electrode materials for Solid Oxide Cells. Auto-combustion synthesis allowed to obtain fine oxide powders up to a Cu content of x = 0.75 under ambient pressure. Investigations of the crystal structure, oxygen deficiency, chemical and thermal stability, as well as...

Combinatorial substrate epitaxy (CSE) was used to study the orientation relationships (ORs) and polytypic stability of AEMnO3 (AE = Ca, Sr) thin films grown on polycrystalline SrMnO3 and SrTiO3 substrates. SrMnO3 films with the stable four‐layered hexagonal (4H) and metastable three‐layered cubic (3C) structures were also grown on (111) and (100) S...

It is shown that appropriately-doped Cu-based perovskite-type oxides exhibit high catalytic activity toward the oxygen reduction reaction at high temperatures, surprisingly making them suitable candidates for preparation of air electrodes for Solid Oxide Fuel Cells. The proposed substitution in La-sublattice of LaCuO3-δ by Ba and/or Sr (i.e. La4BaC...

SmBaCo0.5Mn1.5O5+δ oxide with Sm-Ba cation-ordered perovskite-type structure is synthesized and examined in relation to whole RBaCo0.5Mn1.5O5+δ series (R: selected rare earth elements). Presence of Sm and 3:1 ratio of Mn to Co allows to balance physicochemical properties of the composition, with moderate thermal expansion coefficient value of 18.70...

Responding to the rapidly increasing demand for efficient energy usage and increased speed and functionality of electronic and spintronic devices, multiferroic oxides have recently emerged as key materials capable of tackling this multifaceted challenge. In this paper, we describe the development of single-site manganese-based multiferroic perovski...

Oxygen storage capacity, structure and thermodynamic stability were studied for hexagonal Y0.7Tb0.3MnO3+δ in oxygen and air to assess its applicability for oxygen separation from air by temperature-swing adsorption process. We show that large amounts of oxygen excess can be reversibly incorporated into and extracted from small particle-size samples...

Belonging to not fully-explored ReBaCo2-xMnxO5+δ system, series of ReBaCoMnO5+δ (Re: selected rare earth elements) oxides having perovskite-type structure is synthesized and studied in terms of their structural properties, oxygen content, stability, thermal expansion and transport properties. Impact of Re3+ on physicochemical properties of the comp...

Due to outstanding room temperature electron mobility, the wide-gap perovskite semiconductor BaSnO3 is of high current interest. Although n doping with Sb and O vacancies has been reported, most work has focused solely on La doping. Here we report bulk single crystals of Ba1−xRxSnO3−δ with R=La,Pr, and Nd, as well as unintentionally doped BaSnO3−δ,...

In this work, a novel series of Mn-containing ReBaCo1.5Mn0.5O5+δ (Re: selected rare earth elements) perovskite-type oxides is studied, with systematic measurements of the physicochemical properties reported. Comparison with the very well-studied, parent ReBaCo2O5+δ allows to determine role of the introduced manganese concerning modification of the...

Chromium (VI) is carcinogenic through intermediates formed in the cellular milieu by reduction with small reductants like glutathione (GSH), ascorbate, cysteine, and NADPH. Although the reduction of chromate by thiols has been investigated, the participation of Cr(IV) intermediates has been inferred only indirectly due to the Cr(IV) refractive beha...

We report the structure-property phase diagram of unique single-ion type-1 multiferroic pseudocubic Sr1−xBaxMnO3 perovskites. Employing a specially designed multistep reduction-oxidation synthesis technique, we have synthesized Sr1−xBaxMnO3 compositions in their polycrystalline form with a significantly extended Ba solubility limit that is only riv...

The 3rd Polish-US Workshop on Superconductivity and Magnetism of Advanced Materials, held at Lądek Zdrój in Poland, July 14-19, 2002; Proceedings: Physica C 387 (Nos.1&2), 1 May 2003, Eds.: P.W. Klamut, G.W. Crabtree, T. Kopeć, A.J. Zaleski, J. Klamut, R. Puźniak, H. Szymczak, O. Chmaissem, B. Dąbrowski, B. Janko

Gordon Research Conf. Superconductivity held at Ventura, CA, USA, 12 - 17 January, 1997

The 2nd Polish-US Conference held at Wrocław and Karpacz, Poland, 17-21 August 1998; Proceedings: New Developments in High Temperature Superconductivity, Springer LNP 545, Eds. J. Klamut, B.W. Veal, B.M. Dabrowski, P.W. Klamut, M. Kazimierski

part of the presentation at the American Physical Society March Meeting held at Indianapolis, IN, USA, 18-22 March, 2002 (here at the Q16.009, Focus Session on Magnetoresistive Oxides: Cobaltates and Ruthenates, oral presentation of Yasuo Ito, Northern Illinois University), NSF Grant No. DMR-0105398, project period: 07/01/2001 - 06/30/2004

part of the presentation at the American Physical Society March Meeting held at Indianapolis, IN, USA, 18-22 March, 2002 (here at the J12.001, Focus Session: Synthesis and Structure of High-Tc Superconductors, oral presentation of Michael Maxwell, Northern Illinois University), NSF Grant No. DMR-0105398, project period: 07/01/2001 - 06/30/2004

Comprehensive study of magnetic properties of the layer-ordered perovskites Nd1–xCaxBa1–yLayCo2O5+δ is presented as a function of the site-selected charge doping [c=(x–y)/2+δ−0.5,x≤0.2 and y≤0.1,0.07<δ<0.84], oxygen disorder, and hydrostatic pressure P<10kbar. The single-phase oxygen-ordered orthorhombic phase exhibiting complex ferrimagnetic, anti...

Hexagonal YMnO3+δ is shown to be an effective temperature-swing oxygen storage material working at low temperatures (150–300 °C) in pure oxygen if adequately processed or obtained having sub-micrometer primary particles with limited number of big agglomerates. A substantial increase of a practical oxygen storage capacity is observed for a sample sy...

Structural and thermoelectric properties are reported for a specially designed class of A-site substituted perovskite titanates, (Sr1−x−yCaxNdy)TiO3. Two series synthesized with various A-site Sr-rich or Ca-rich (Sr-poor) concentrations were investigated using high-resolution neutron powder diffraction as a function of temperature and Nd doping. Ea...

Resonant soft X-ray scattering was used to determine the presence of more subtle orderings not detected in standard structural analyses. By tuning to specific Co absorption edges, arrangements particular to the electronic states of those elements are enhanced. We have discovered an ordering commensurate to the lattice at the ($\frac{1}{4}~\frac{1}{...

Structural and oxygen content changes of hexagonal HoMnO3+δ manganite at the stability boundary in the perovskite phase have been studied by X-ray diffraction and thermogravimetry using in situ oxidation and reduction processes at elevated temperatures in oxygen and air. The oxygen storage properties during structural transformation between stoichi...

The structural phase transition in hexagonal BaMnO$_3$ occurring at $T_c$=130 K was studied in ceramic samples using electron and X-ray diffraction, second harmonic generation as well as by dielectric and lattice dynamic spectroscopies. The low-temperature phase (space group $P6_{3}cm$) is ferroelectric with a triplicated unit cell. The phase trans...

An exchange bias (EB) effect was observed in mixed valent LaxBa1−xFeO3 (x = 0.125, 0.25, 0.33) perovskites exhibiting the antiferromagnetic (AFM) helical order among Fe4+ ions coexisting with the ferromagnetic (FM) cluster phase in the ground state. The La3+ ions for Ba2+ site substitution, associated with increase in number of the AFM coupled Fe3+...

Mixed perovskites Sr 1−x Ba x MnO 3 were lately indicated as possible multiferroics with a strong magnetoelectric coupling. However, THz spectroscopy with varying temperature and magnetic field revealed no magnetodielectric effect. Our study brings new information on the ferroelectric phase transition.

A ⁵⁹Co spin-echo nuclear magnetic resonance (NMR) study, along with complimentary magnetization and x-ray diffraction characterization, is reported for three of the four magnetic line phases which occur in the hole-doped perovskite system SrCoOx, 2.5 ≤ x ≤ 3. The magnetic line phases are the single-valence state end-member compounds SrCoO2.5 and Sr...

Two magnetic phase transitions have been noted for SrCoO3−y for near-stoichiometric oxygen concentrations (small y). Using muon-spin rotation and neutron scattering experiments, we have established that the two transitions represent separate, spatially distinct magnetic phases that coexist in a two-phase equilibrium mixture. The two phases most lik...

The spin susceptibility of the localized Mn(t2g) electrons, χs, and the spatially distributed spin density of the doped electrons were investigated by O17 nuclear magnetic resonance (NMR) in the paramagnetic (PM) and antiferromagnetic (AF) phases of electron-doped SrMnO3−x ceramics with the cubic structure. Three lightly doped samples (2x<0.015) we...

Dielectric response of perovskite Sr1-x Ba x MnO3 (x = 0.43 and 0.45) ceramics was investigated using microwave, THz and infrared spectroscopic techniques in order to study the ferroelectric and antiferromagnetic phase transitions with critical temperatures T C ≈ 350 K and T N ≈ 200 K, respectively. The two lowest-frequency polar phonons are overda...

Layered cobaltites RBaCo2 O5.5, considered for application as cathodes of fuel cells, exhibit a rich spectrum of magnetic and electronic properties. Taking advantage of the fact that Nd3+ and Ca2+ ions have nearly identical ionic radii, by synthesizing the Nd1−x CaxBaCo2 O5.5 compounds (for x= 0, 0.02, 0.06, 0.08, 0.16, and 0.2), a hole doping was...

Crystal structure, oxygen storage-related and preliminary anaerobic methane combustion studies were conducted for BaY1 − xGdxMn2O5 + δ (0, 0.25, 0.5, 0.75 and 1) series of oxides prepared by a sol–gel method. All samples were found to possess layered-type A-site cation ordering, with the unit cell volume linearly dependent on the average radius of...

Magnetic properties of bulk polycrystalline Mn-doped SrRu1−xMnxO3 perovskite, at doping range 0.2 ≤ x ≤ 0.3, were studied by both magnetization and ac-susceptibility measurements. It was found that the exchange bias (EB) effect emerges with increasing Mn doping in SrRu1−xMnxO3 at x ≈ 0.25, following the ferromagnetic (FM) to antiferromagnetic (AFM)...

Two magnetic phase transitions have been noted for SrCoO$_{3-y}$ for near-stoichiometric oxygen concentrations (small y). Using muon spin rotation and neutron scattering experiments, we have established that the two transitions represent separate, spatially distinct magnetic phases that coexist in a two-phase equilibrium mixture. The two phases mos...

The authors note that the author name S. A. Sabok should instead appear as S. A. Sabok-Sayr. The corrected author line appears below. The online version has been corrected.

Single-phase polycrystalline samples of stoichiometric RMnO3+δ (R = Er, Y, and Ho) were achieved in the hexagonal P63cm structure through solid state reaction at ∼1300 °C. Thermogravimetric measurements in oxygen atmospheres demonstrated that samples with the larger Ho and Y show rapid and reversible incorporation of large amounts of excess oxygen...

The normal state in the hole underdoped copper oxide superconductors has proven to be a source of mystery for decades. The measurement of a small Fermi surface by quantum oscillations on suppression of superconductivity by high applied magnetic fields, together with complementary spectroscopic measurements in the hole underdoped copper oxide superc...

In this paper we report on crystal structure and oxygen storage properties of A-site cation ordered BaLnMn2O5+δ (Ln: Pr, Nd, Sm, Gd, Dy, Er and Y) perovskite-type oxides. The materials show practically complete and reversible change between fully reduced BaLnMn2O5 and oxidized BaLnMn2O6, which occurs at moderate temperatures (300–500 °C) during cha...

Structural, thermoelectric and magnetic properties of NdBa2+1−yLa3+yCo2O5+δ (y = 0.06) were investigated over a wide range of oxygen content 0.26 < δ < 0.90. The single-phase orthorhombic samples with ordered planes of the 5- and 6-coordinated to oxygen cobalt ions were obtained and studied for 0.45 < δ < 0.55. It was found that the Seebeck coeffic...

The crystal structure of PrInO33 was investigated in the temperature range 303 -1123 K by high-resolution neutron-powder diffraction. The PrInO3 adopts highly distorted variant of the perovskite structure with orthorhombic Pnma space group in the whole temperature range investigated. The bond length and bond-angle analysis revealed very slow tenden...

The electronic structures of SrMn1 -xRuxO3 (0 ≤x ≤1 ) have been investigated by employing soft x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD). Both Mn and Ru ions are nearly tetravalent (Mn4 +,Ru4 +) for the end members of x =0 (SrMnO3) and x =1 (SrRuO3). In the Ru-dilute concentration (x ≤̃0.2 ) , Ru ions are...

The magnetic order, spin dynamics, and crystal structure of the multiferroic Sr0.56Ba0.44MnO3 have been investigated using neutron and x-ray scattering. Ferroelectricity develops at TC=305 K with a polarization of 4.2 microC/cm2 associated with the displacements of the Mn ions, while the Mn4+ spins order below TN = 200 K into a simple G-type commen...

Single-phase polycrystalline samples of hexagonal Dy1-xYxMnO3+delta were synthesized over the full solubility range under reducing oxygen partial pressure conditions. Rietveld refinements using neutron powder diffraction data (NPD) confirmed the persistence of the parent hexagonal P(63)cm (Space group #185) structure for all the stoichiometric (del...

The absence of the antiferromagnetic order in Nd0.9Ca0.1BaCo2O5.5 has been found to remain unchanged by applying a hydrostatic pressure of 10 kbar. In magnetic studies of polycrystalline Nd0.9Ca0.1BaCo2O5+δ (δ = 0.07 - 0.69), we have found a reappearance of the antiferromagnetic phase, caused by an increase in oxygen index δ above 0.51 related to e...

The study of oxygen vacancy ordering in the LaxSr1-xMnOy system has shown a strong correlation between Mn formal valence and coordination to oxygen. The Mn2+ was found forming octahedra (Oc) and tetrahedra (Te), Mn3+ octahedra and pyramids (Py) and Mn4+ only octahedra. This tendency was derived from the presence of three kinds of vacancy orderings...

Magnetic measurements have been performed under pressure of 0–9.7 kbar and in the temperature range of 5–300 K for the hole-doped Nd1-xCaxBaCo2O5.5 system over the composition range x = 0–0.06, where a strong competition between antiferromagnetic and ferrimagnetic phases is present. The dependence of TN, i.e., of the temperature of a first order ph...

In this paper we report on oxygen storage-related properties of selected Co- and Fe-containing perovskite-type oxides, and analyze their advantages and disadvantages in relation to the Mn-based, A-site ordered BaYMn2O5 + δ system. In particular, the crystal structure of reduced and oxidized Ln0.5A′0.5Co0.5Fe0.5O3 − δ (Ln: La, Sm; A′: Sr, Ba) and La...

The interaction between the transition metal 3d and the oxygen 2p states via hybridization underpins many of the phenomena in transition metal oxide materials. We report the empirical trend of this interaction using the pre-edge feature of the O K-edge X-ray absorption spectrum. Our assessment method is built on the dipole approximation and the con...

Ceramics, which exhibit high proton conductivity at moderate temperatures, are studied as electrolyte membranes or electrode components of fuel cells, electrolysers or CO 2 converters. In severe operating conditions (high gas pressure/high temperature), the chemical activity towards potentially reactive atmospheres (water, CO 2 , etc.) is enhanced....

BaErMn2O5 is synthesized from the respective nitrates dissolved in a minimal amount of water using the ammonia salt of EDTA as a complexing agent (Ar flow, 1200 °C, 8 h, <95 wt.% yield).

In this paper, we report on a synthesis procedure, structural and electrical properties of BaErMn2O5 and BaErMn2O6, A-site double perovskites having layered arrangement of Ba and Er cations. These materials belong to a family of BaLnMn2O5+δ oxides, which up to now were successfully synthesized for Ln=Y and La–Ho lanthanides. Up to our knowledge, th...

Fe-doping (up to 11 mole%) into SrRuO3 (SRO) thin films on SrTiO3 substrates decreased correlation lengths of both surface and interface. It turned out that Fe was doped in the valence state of 3+ without formation of the Fe2O3 phase, which caused orthorhombic distortion. T C values decreased from 145 K to 97 K with increasing Fe concentration (C F...

Using pulsed laser deposition and a unique fast quenching method, we have prepared SrCoOx epitaxial films on SiTiO3 substrates. As electrochemical oxidation increases the oxygen content from x = 2.75 to 3.0, the films tend to favor the discrete magnetic phases seen in bulk samples for the homologous series SrCoO(3-n/8) (n = 0, 1, 2). Unlike bulk sa...