In the present work, the structural, magnetic, and electronic properties of the two- and one-dimensional honeycomb structures of recently synthesized MnO [Zhang et al. Nat. Commun., 20, 1073-1078 (2021)] are investigated by using first principles calculations. Our calculations show that the single layer 2D MnO crystal has a degenerate antiferromagnetic (AFM) ground state and a relatively less favorable ferromagnetic (FM) state. In addition, magnetic anisotropy calculations unveil that the easy-axis direction for magnetism originating from unpaired electron states in manganese atoms is normal to the crystal plane. Electronically, while the FM-MnO is a direct semiconductor with a narrow bandgap, AFM phases display large indirect bandgap semiconducting behavior. Moreover, calculations on nanoribbons of MnO reveal that zigzag edged ribbons display metallic bahavior, whereas armchair edged nanoribbons are semiconductors. Magnetically, for both zigzag- or armchair-edged nanoribbons, AFM order perpendicular to the nanoribbon growth direction is found to be favorable over the other AFM and FM orders. Moreover, depending on the edge symmetry and ribbon width, forbidden band gap values of nanoribbons display distinct family behaviors.
Manganese oxide nanosheets were synthesized using liquid phase exfoliation that achieved suspensions in isopropanol with concentrations of up to 0.45 mg/ml. A study of solubility parameters showed that the exfoliation was optimum in DMF followed by isopropanol and diethylene glycol. Isopropanol was the solvent of choice due to its environmentally friendly nature and ease of use for further processing. The 2D hybrid was synthesized in isopropanol suspensions with concentrations of up to 0.5 mg/ml and demonstrated stability against reaggregation for up to six months. The coexfoliation was found …
X-ray amorphous manganese oxides were prepared by reduction of sodium permanganate by lithium iodide in aqueous medium (MnOx-I) and by decomposition of manganese carbonate at moderate temperature (MnOx-C). TEM showed that these materials are not amorphous, but nanostructured, with a prominent spinel substructure in MnOx-C. These materials intercalate lithium with capacities up to 200 mAh/g at first cycle (potential window 1.8-4.3 V) and 175 mAh/g at 100th cycle. Best performances for MnOx-C are obtained with cobalt doping. Potential electrochemical spectroscopy shows that the initial discharge…
Results of quantum mechanical simulations of the influence of edge disorder on transport in graphene nanoribbon metal oxide semiconductor field-effect transistors (MOSFETs) are reported. The addition of edge disorder significantly reduces ON-state currents and increases OFF-state currents, and introduces wide variability across devices. These effects decrease as ribbon widths increase and as edges become smoother. However the bandgap decreases with increasing width, thereby increasing the band-to-band tunneling mediated subthreshold leakage current even with perfect nanoribbons. These results …
We present an analysis of the polymorphic energy ordering and properties of the rock salt and zincblende structures of manganese oxide using fixed node diffusion Monte Carlo (DMC). Manganese oxide is a correlated, antiferromagnetic material that has proven to be challenging to model from first principles across a variety of approaches. Unlike conventional density functional theory and some hybrid functionals, fixed node diffusion Monte Carlo finds the rock salt structure to be more stable than the zincblende structure, and thus recovers the correct energy ordering. Analysis of the site-resolve…
Atom probe tomography is routinely used for the characterisation of materials microstructures usually assuming that the microstructure is unaltered by the analysis. When analysing ionic conductors, however, gradients in the chemical potential and the electric field penetrating dielectric atom probe specimens can cause significant ionic mobility. While ionic mobility is undesired when aiming for materials characterisation it offers a strategy to manipulate materials directly in-situ in the atom probe. Here, we present experimental results on the analysis of the ionic conductor Lithium-Manganese…
A new minimal model is constructed for the doped manganese oxides which exhibit colossal magnetoresistance (CMR), involving broad spin-majority conduction band as well as nearly localised spin-minority electron states. A simple mean field analysis yields a temperature-dependent hybridised band structure with suppressed carrier weight at the Fermi level. Spin stiffness is complex, indicating unusually strong spin wave damping. Experimental and theoretical investigations are needed to further verify the relevance of the proposed model.
Two-dimensional manganese oxide layers have been grown on Pd(100) and have been characterized by scanning tunnelling microscopy (STM), low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). The complex surface phase diagram of MnOx on Pd(100) is reported, where nine different novel Mn oxide phases have been detected as a function of the chemical potential of oxygen mO. Three regions of the chemical potential of oxygen can be identified, in which structurally related oxide phases are formed, often in coexistence at the surface. The different regions of mO are reflect…
The structure and magnetic properties of oligonuclear manganese complex [Mn(hfa)2cpo]2 (where hfa is hexafluoroacetylacetonate dehydrate and cpo is 4-cyanopyridine-N-oxide) are presented. In the unit cell, the dinuclear molecules are well isolated from each other. The non-monotonous dependence of magnetic susceptibility is explained in terms of the hierarchy of exchange parameters by using exact diagonalization. The thermodynamic behavior of pure cpo and [Mn(hfa)2(cpo)]2 is simulated numerically in a dimer approximation by an extrapolation to spin S = 5/2. The Mn-Mn exchange integral is evalua…
The electronic structure is found to be understandable in terms of free-atom term values and universal interorbital coupling parameters, since self-consistent tight-binding calculations indicate that Coulomb shifts of the d-state energies are small. Special-point averages over the bands are seen to be equivalent to treatment of local octahedral clusters. The cohesive energy per manganese for MnO, Mn2O3, and MnO2, in which manganese exists in valence states Mn2+, Mn3+, and Mn4+, is very nearly the same and dominated by the transfer of manganese s electrons to oxygen p states. There are small co…
We performed a systematic study of soft X-ray absorption spectroscopy in various manganese oxides and fluorides. Both Mn L-edges and ligand (O and F) K-edges are presented and compared with each other. Despite the distinct crystal structure and covalent/ionic nature in different systems, the Mn-L spectra fingerprint the Mn valence and spin states through spectral lineshape and energy position consistently and evidently. The clear O- and F- K pre-edge features in our high resolution spectra enable a quantitative definition of the molecular orbital diagram with different Mn valence. In addition,…
Effectiveness of galaxite (Al2O3MnO) and manganese oxide (MnO2) in nucleating acicular ferrite was demonstrated in a steel with composition of Fe-13.92Mn-4.53Al-1.28Si-0.11C. The hot rolled and quenched steel had a duplex microstructure of delta-ferrite and partially transformed austenite. Thermal treatments were used to manipulate the concentration and type of oxides and the ferrite plate density was found to correlate with inclusions of low misfit. Both bainitic and acicular ferrite were observed and the prior austenite had a grain diameter of 16.5 micrometers. Upon tensile testing the retai…
Unraveling the atomistic and the electronic structure of solid-liquid interfaces is the key to the design of new materials for many important applications, from heterogeneous catalysis to battery technology. Density functional theory (DFT) calculations can in principle provide a reliable description of such interfaces, but the high computational costs severely restrict the accessible time and length scales. Here, we report machine learning-driven simulations of various interfaces between water and lithium manganese oxide (Li$_x$Mn$_2$O$_4$), an important electrode material in lithium ion batte…
Through direct nanoparticle nucleation and growth on nitrogen doped, reduced graphene oxide sheets and cation substitution of spinel Co3O4 nanoparticles, a manganese-cobalt spinel MnCo2O4/graphene hybrid was developed as a highly efficient electrocatalyst for oxygen reduction reaction (ORR) in alkaline conditions. Electrochemical and X-ray near edge structure (XANES) investigations revealed that the nucleation and growth method for forming inorganic-nanocarbon hybrid results in covalent coupling between spinel oxide nanoparticles and N-doped reduced graphene oxide (N-rmGO) sheets. Carbon K-edg…
A new mechanism is proposed to explain the colossal magnetoresistance and related phenomena. Moving electrons accompanied by Jahn-Teller phonon and spin-wave clouds may form composite polarons in ferromagnetic narrow-band manganites. The ground-state and finite-temperature properties of such composite polarons are studied in the present paper. By using a variational method, it is shown that the energy of the system at zero temperature decreases with the formation of composite polaron; the energy spectrum and effective mass of the composite polaron at finite temperature is found to be strongly …
Ferroelectric oxides have attracted much attention due to their wide range of applications, especially in electronic devices such as nonvolatile memories and tunnel junctions. As a result, the monolithic integration of these materials into silicon technology and its nanostructuration to develop alternative cost-effective processes are among the central points in current technology. In this work, we used a chemical route to obtain nanowire thin films of a novel Sr1+δMn8O16 (SMO) hollandite-type manganese oxide on silicon. Scanning transmission electron microscopy combined with crystallographic …
Rational combination holds the key for non-precious metal oxides and economic carbon materials to the creation of high performance air electrode materials. Carbon nanotubes (CNTs)-supported manganese oxides composite catalysts (CMnCs) were obtained by reacting commercial CNTs with MnO$_4^-$ in diluted H$_2$SO$_4$ with cancelling conventional hydrothermal processing or adding surfantant templates. CMnCs were then assembled into commercial air cathodes equipped in metal air fuel cells. CNTs demonstrated structurally much defective. Outer CNT walls were cracked into graphene nano pieces yet remai…
Field-induced magnetization jumps with similar characteristics are observed at low temperature for the intermetallic germanide Gd5Ge4and the mixed-valent manganite Pr0.6Ca0.4Mn0.96Ga0.04O3. We report that the field location -and even the existence- of these jumps depends critically on the magnetic field sweep rate used to record the data. It is proposed that, for both compounds, the martensitic character of their antiferromagnetic-to-ferromagnetic transitions is at the origin of the magnetization steps.
Manganese oxide-coated TiO2 nanotube array (NTA) was synthesized and applied for the (electro)catalytic oxidation of sulfide. By setting the electrodeposition parameters and calcination temperature, the coating obtained was MnO2 or Mn2O3, with rod or needle like morphology. Excellent catalytic activity of the Ti/TiO2 NTA/MnxOy anodes resulted in robust and selective oxidation of sulfide to elemental sulfur via an inner sphere complex between the sulfide ion and Mn-oxide. The penetration of the MnxOy inside the NTA improved adhesion and enhanced the electron transfer, thus enabling complete and…
We point out that the existing experimental data of most manganese oxides show the {\sl frustrated} p-wave superconducting condensation in the ferromagnetic phase in the sense that the superconducting coherence is not long enough to cover the whole system. The superconducting state is similar to the $A_{1}$ state in superfluid He-3. The sharp drop of resistivity, the steep jump of specific heat, and the gap opening in tunneling are well understood in terms of the p-wave pairing. In addition, colossal magnetoresistance (CMR) is naturally explained by the superconducting fluctuations with increa…
We present results of an approach to incorporate redox-active manganese oxide into the 3-dimensional porous structure of carbon xerogels under self-limiting electroless conditions. By varying the structure of the carbon backbone, we found that deposition of manganese oxide preferably takes place on the external surface area of the carbon xerogels. From our detailed analysis we conclude that 3-dimensional carbon xerogels with particle and pore sizes ranging from 10 to 20 nm and low manganese oxide precursor concentration combined with long deposition times are beneficial for fast operating pseu…
Many positive electrode materials in lithium ion batteries include transition metals which are difficult to describe by electronic structure methods like density functional theory (DFT) due to the presence of multiple oxidation states. A prominent example is the lithium manganese oxide spinel Li$_x$Mn$_2$O$_4$ with $0\leq x\leq2$. While DFT, employing the local hybrid functional PBE0r, provides a reliable description, the need for extended computer simulations of large structural models remains a significant challenge. Here, we close this gap by constructing a DFT-based high-dimensional neural…
The lithium manganese oxide spinel Li$_x$Mn$_2$O$_4$, with $0\leq x\leq 2$, is an important example for cathode materials in lithium ion batteries. However, an accurate description of Li$_x$Mn$_2$O$_4$ by first-principles methods like density functional theory is far from trivial due to its complex electronic structure, with a variety of energetically close electronic and magnetic states. It was found that the local density approximation as well as the generalized gradient approximation (GGA) are unable to describe Li$_x$Mn$_2$O$_4$ correctly. Here, we report an extensive benchmark for differe…
We report a novel synthesis route of homogeneously manganese-doped titanium dioxide nanotubes in a broad concentration range. The scroll-type trititanate (H(2)Ti(3)O(7)) nanotubes prepared by hydrothermal synthesis were used as precursors. Mn2+ ions were introduced by an ion exchange method resulting Mn(x)H(2-x)Ti(3)O(7). In a subsequent heat-treatment they were transformed into Mn(y)Ti(1-y)O(2) where y=x/(3+x). The state and the local environment of the Mn2+ ions in the precursor and final products were studied by Electron Spin Resonance (ESR) technique. It was found that the Mn2+ ions occupy…
Layered LiMnO$_2$ and Li$_2$MnO$_3$ are of great interest for lithium-ion battery cathodes because of their high theoretical capacities. The practical application of these materials is, however, limited due to poor electrochemical performance. We herein report a comprehensive first-principles study of defect physics in LiMnO$_2$ and Li$_2$MnO$_3$ using hybrid-density functional calculations. We find that manganese antisites have low formation energies in LiMnO$_2$ and may act as nucleation sites for the formation of impurity phases. The antisites can also occur with high concentrations in Li$_…
We describe the ground- and excited-state electronic structure of bulk MnO and NiO, two prototypical correlated electron materials, using coupled cluster theory with single and double excitations (CCSD). As a corollary, this work also reports the first implementation of unrestricted periodic ab initio equation-of motion CCSD. Starting from a Hartree-Fock reference, we find fundamental gaps of 3.46 eV and 4.83 eV for MnO and NiO respectively for the 16 unit supercell, slightly overestimated compared to experiment, although finite-size scaling suggests that the gap is more severely overestimated…
Ruderman-Kittel-Kasuya-Yosida interaction even if their wave functions lack direct overlap. Theory predicts that spin-orbit scattering leads to a Dzyaloshinskii-Moriya type enhancement of this indirect exchange interaction, giving rise to chiral exchange terms. Here we present a combined spin-polarized scanning tunneling microscopy, angle-resolved photoemission, and density functional theory study of MnO$_2$ chains on Ir(100). Whereas we find antiferromagnetic Mn--Mn coupling along the chain, the inter-chain coupling across the non-magnetic Ir substrate turns out to be chiral with a $120^{\cir…
Structural analysis of a layered manganese tungstate diaminoalkane hybrid series suggests that this compound forms a spin-5/2 spin-ladder structure. We use X-ray diffraction, electron microscopy and x-ray absorption spectroscopy results to infer the structure. DC magnetization of the manganese compound and a possible copper analogue appear to show that the manganese system behaves like 1-dimensional antiferromagnetic Heisenberg chains (i.e. $J_{\parallel} \gg J_{\perp})$ while the copper system is fitted well by a $S = {1/2}$ spin ladder model, giving the parameters $g = 1.920 \pm 0.008$, $J_{…
Electrical current can be completely spin polarized in a class of materials known as half-metals, as a result of the coexistence of metallic nature for electrons with one spin orientation and insulating for electrons with the other. Such asymmetric electronic states for the different spins have been predicted for some ferromagnetic metals - for example, the Heusler compounds- and were first observed in a manganese perovskite. In view of the potential for use of this property in realizing spin-based electronics, substantial efforts have been made to search for half-metallic materials. However, …
We present a first-principles study of the atomic, electronic, and magnetic properties of two-dimensional (2D), single and bilayer ZnO in honeycomb structure and its armchair and zigzag nanoribbons. In order to reveal the dimensionality effects, our study includes also bulk ZnO in wurtzite, zincblende, and hexagonal structures. The stability of 2D ZnO, its nanoribbons and flakes are analyzed by phonon frequency, as well as by finite temperature ab initio molecular-dynamics calculations. 2D ZnO in honeycomb structure and its armchair nanoribbons are nonmagnetic semiconductors but acquire net ma…
Mn is used as a dopant to improve the electromechanical properties of perovskite oxides. We elucidate the role of Mn defects and associated vacancies on the electronic, atomic and ferroelectric properties of BaTiO$_3$. Using density functional theory (DFT) and DFT+U we investigate the equilibrium geometry and electronic properties of Mn ion on A or B sites and with compensating oxygen vacancies. We study the change in the oxidation state of Mn in response to local environment changes, such as the presence of oxygen vacancies.
Manganese oxides have received much attention over the years among the wide range of electrocatalysts for the oxygen evolution reaction (OER) due to their low toxicity, high abundance and rich redox chemistry. While many previous studies focused on the activity of these materials, a better understanding of the material transformations relating to activation or degradation is highly desirable, both from a scientific perspective and for applications. We electrodeposited Na-containing MnOx without long-range order from an alkaline solution to investigate these aspects by cyclic voltammetry, scann…
In this work, we demonstrate atomic-layer-deposited (ALD) single-channel indium oxide (In2O3) gate-all-around (GAA) nanoribbon FETs in a back-end-of-line (BEOL) compatible process. A maximum on-state current (ION) of 19.3 mA/μm (near 20 mA/μm) is achieved in an In2O3 GAA nanoribbon FET with a channel thickness (TIO) of 3.1 nm, channel length (Lch) of 40 nm, channel width (Wch) of 30 nm and dielectric HfO2 of 5 nm. The record high drain current obtained from an In2O3 FET is about one order of magnitude higher than any conventional single-channel semiconductor FETs. This extraordinary drain curr…
Lithium ion batteries often contain transition metal oxides like Li$_{x}$Mn$_2$O$_4$ ($0\leq x\leq2$). Depending on the Li content different ratios of Mn$^\text{III}$ to Mn$^\text{IV}$ ions are present. In combination with electron hopping the Jahn-Teller distortions of the Mn$^\text{III}$O$_6$ octahedra can give rise to complex phenomena like structural transitions and conductance. While for small model systems oxidation and spin states can be determined using density functional theory (DFT), the investigation of dynamical phenomena by DFT is too demanding. Previously, we have shown that a hi…
We study the channel width scaling of back-gated MoS2 metal-oxide-semiconductor field-effect transistors (MOSFETs) from 2 μm down to 60 nm. We reveal that the channel conductance scales linearly with channel width, indicating no evident edge damage for MoS2 nanoribbons with widths down to 60 nm as defined by plasma dry etching. However, these transistors show a strong positive threshold voltage (VT) shift with narrow channel widths of less than 200 nm. Our results also show that transistors with thinner channel thicknesses have larger VT shifts associated with width scaling. Devices fabricated…
In sharp contrast to molecular synthesis, materials synthesis is generally presumed to lack selectivity. The few known methods of designing selectivity in solid-state reactions have limited scope, such as topotactic reactions or strain stabilization. This contribution describes a general approach for searching large chemical spaces to identify selective reactions. This novel approach explains the ability of a nominally "innocent" Na$_2$CO$_3$ precursor to enable the metathesis synthesis of single-phase Y$_2$Mn$_2$O$_7$ -- an outcome that was previously only accomplished at extreme pressures an…
Using local-probe magnetic-characterization techniques of muon spin relaxation ($μ$SR) and electron spin resonance (ESR) we have investigated the Mn-induced magnetism of the wide-bandgap perovskite SrTiO$_3$. Our results clearly demonstrate that this diluted magnetic oxide (DMO) remains paramagnetic down to low temperatures for both doping cases, i.e., when Mn substitutes for Sr or Ti. In addition, both experimental techniques have unveiled that the distribution of individual Mn$^{2+}$ and Mn$^{4+}$ ions is nonrandom, as these ions partially aggregate into nanosized clusters.
With photothermal efficiency higher than traditionally used reduced graphene oxide, while simultaneously being water dispersible, we propose biocompatible Molybdenum Nanoribbons - gold Nanoparticles (MoS2 NR-Au NPs) system for synergistically enhanced photo-thermal ablation of cancerous cells (100% fatality) using NIR radiation (808nm), owing to commendable temperature rise above 70oC at a much faster rate.
We report on a theoretical study of electromagnetic properties of zigzag magnesium oxides nanoribbons (Z-MgONRs). We propose that the polar charges and the spin polarization are the two key factors for edge magnetism. Based on first-principle calculations, we demonstrate that both O- and Mg-edges are magnetic and their magnetic moments all can be efficiently modulated via external electric field.And the edge magnetism is further studied in the framework of effective tight-binding model, which provides a starting point for the calculation of one particle Green's function and the determination o…
Incorporation of magnetism in graphene based compounds holds great promise for potential spintronic applications. By optimizing point defects and high edge density of defects, we report many-fold increase in the ferromagnetic saturation moment in lacey reduced graphene oxide nanoribbons (LRGONR) as compared to other graphene derivatives. The samples were synthesized using chemical unzipping methodology. Detailed structural and morphological characterizations are discussed that include XRD, Raman, SEM, HRTEM and XPS measurements. Brilluoin function analysis to magnetization data reflects best f…
High-spin paramagnetic manganese defects in polar piezoelectric zinc oxide exhibit a simple almost axial anisotropy and phase coherence times of the order of a millisecond at low temperatures. The anisotropy energy is tunable using an externally applied electric field. This can be used to control electrically the phase of spin superpositions and to drive spin transitions with resonant microwave electric fields.
Driven by interactions due to the charge, spin, orbital, and lattice degrees of freedom, nanoscale inhomogeneity has emerged as a new theme for materials with novel properties near multiphase boundaries. As vividly demonstrated in complex metal oxides and chalcogenides, these microscopic phases are of great scientific and technological importance for research in high-temperature superconductors, colossal magnetoresistance effect, phase-change memories, and domain switching operations. Direct imaging on dielectric properties of these local phases, however, presents a big challenge for existing …
We report a first-principles study of defect thermodynamics and transport in spinel-type lithium manganese oxide LiMn$_2$O$_4$, an important lithium-ion battery electrode material, using density-functional theory and the Heyd-Scuseria-Ernzerhof screened hybrid functional. We find that intrinsic point defects in LiMn$_2$O$_4$ have low formation energies and hence can occur with high concentrations. The electronic conduction proceeds via hopping of small polarons and the ionic conduction occurs via lithium vacancy and/or interstitialcy migration mechanisms. The total conductivity is dominated by…
We perform density functional theory plus dynamical mean field theory calculations to investi- gate internal charge transfer in an artificial superlattice composed of alternating layers of vanadate and manganite perovskite and Ruddlesden-Popper structure materials. We show that the elec- tronegativity difference between vanadium and manganese causes moderate charge transfer from VO2 to MnO2 layers in both perovskite and Ruddlesden-Popper based superlattices, leading to hole doping of the VO2 layer and electron doping of the MnO2 layer. Comparison of the perovskite and Ruddlesden-Popper based h…
Electronic structure of the manganese oxide solid is studied by the quantum Monte Carlo (QMC) methods. The trial wavefunctions are built using orbitals from unrestricted Hartree-Fock and Density Functional Theory, and the electron-electron correlation is recovered by the fixed-node QMC. The correlation effects are significant and QMC estimations of the gap and cohesion show a very good agreement with experiment. Comparison with hybrid functional results points out the importance of the exact exchange for improvement of the Density Functional description of transition metal oxide systems.
Structural and magnetic properties have been studied for polycrystalline Zn_1-xMn_xO (x=0.02, 0.03, 0.05). Low-temperature (~500 oC) synthesis leaves unreacted starting ZnO and manganese oxides. Contrary to a recent report, no bulk ferromagnetism was observed for single-phase materials synthesized in air at temperatures above 900 oC. Single-phase samples show paramagnetic Curie-Weiss behavior.
Materials with strong magnetoresistive responses are the backbone of spintronic technology, magnetic sensors, and hard drives. Among them, manganese oxides with a mixed valence and a cubic perovskite structure stand out due to their colossal magnetoresistance (CMR). A double exchange interaction underlies the CMR in manganates, whereby charge transport is enhanced when the spins on neighboring Mn3+ and Mn4+ ions are parallel. Prior efforts to find different materials or mechanisms for CMR resulted in a much smaller effect. Here we show an enormous CMR at low temperatures in EuCd2P2 without man…
We adopt a broken-symmetry strategy for evaluating effective magnetic constants $J$ within the fully self-consistent GW method. To understand the degree of spin contamination present in broken-symmetry periodic solutions, we propose several size-extensive quantities that demonstrate that the unrestricted self-consistent GW preserves well the broken-symmetry character of the unrestricted Hartree--Fock solutions. The extracted $J$ are close to the ones obtained from multireference wave-function calculations. In this paper, we establish a robust computational procedure for finding magnetic coupli…
We investigate a series of manganese oxides, the La0.225Pr0.4(Ca1-xSrx)0.375MnO3 system. The x = 0 sample is a prototype compound for the study of phase separation in manganites, where ferromagnetic and charge ordered antiferromagnetic phases coexist. Replacing Ca2+ by Sr2+ gradually turns the system into a homogeneous ferromagnet. Our results show that the material structure plays a major role in the observed magnetic properties. On cooling, at temperatures below 100 K, a strong contraction of the lattice is followed by an increase in the magnetization. This is observed both through thermal e…
Investigation of the oxygen-deficient 112-type ordered oxides of the type LnBaCoMnO5+δ(Ln = Nd, Eu) evidences certain unusual magnetic behavior at low temperatures, compared to the LnBaCo2O5+δcobaltites. One observes that the substitution of manganese for cobalt suppresses the ferromagnetic state and induces strong antiferromagnetic interactions. Importantly, NdBaCoMnO5.9 depicts a clear paramagnetic to antiferromagnetic type transition around 220 K, whereas for EuBaCoMnO5.7 one observes an unusual magnetic behavior below 177 K which consists of ferromagnetic regions embedded in an antiferroma…
We report a method for acquiring Foucault images and small-angle electron diffraction patterns in external magnetic fields using a conventional transmission electron microscope without any modification. In the electron optical system that we have constructed, external magnetic fields parallel to the optical axis can be controlled using the objective lens pole piece under weak excitation conditions in the Foucault mode and the diffraction mode. We observe two ferromagnetic perovskite-type manganese oxides, La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ and Nd$_{0.5}$Sr$_{0.5}$MnO$_{3}$, in order to visualize ma…
