Mn O3 Research Articles

The effect of manganese doping and calcination temperature on polarization, structural and magnetic properties of multiferroic LuFe(1-)Mn O3 system

The effect of manganese doping and calcination temperature on polarization, structural and magnetic properties of multiferroic LuFe(1-)Mn O3 system

Visible light in situ driven electron accumulation at the Ti–Mn–O3 sites of TiO2 hollow spheres for photocatalytic hydrogen production

Mn atoms and oxygen vacancies induce the formation of Ti–Mn–O3 sites by visible light-driven, which further regulates the surface potential, visible-light absorption, and carrier separation, resulting in superior H2 evolution.

Exchange interactions in hexagonal YMnO3 and LuMnO3 multiferroic compounds

In this work, spin density functional theory calculations are employed to obtain the exchange interactions in hexagonal YMnO3 and LuMnO3 multiferroic compounds, which have been a matter of debate in the literature. The exchange and correlation electronic effects are approximated using the local spin density approximation (LSDA) with the inclusion of the effective Hubbard U correction (Ueff). The intraplane superexchange interaction (Jnn) decreases with increasing Ueff. Moreover, the Jnn value with the best agreement with experiment is found for Ueff values between 2.55 and 4.0 ​eV. Without the addition of Ueff corrections, i.e., with standard LSDA calculations, the magnitude of Jnn is overestimated. The Bader topological analysis of the electron density at the bond critical point shows that the closed-shell interaction of the Mn–O3 and Mn–O4 bonds in both materials increases with increasing Ueff, which justifies the decrease of Jnn with increasing Ueff.. Additionally, both interplane and intraplane super-superexchange interactions are computed and compared with previous studies.

Mössbauer and magnetic studies of the phase state of SrFe12O19/La0.9Ca0.1MnO3 composites

The formation of an intermediate phase in SrFe12O19/La0.9Ca0.1MnO3 composites was demonstrated for the first time using only Mossbauer spectroscopy. The SrFe12O19/La0.9Ca0.1MnO3 composite was prepared by the two-stage (sol–gel and hydrothermal) synthesis with varying initial conditions. The X-ray diffraction studies showed that the composite consisted of two phases: well-formed structures of manganite La0.9Ca0.1MnO3 and hexagonal ferrite SrFe12O19. It was found that nanocrystalline La0.9Ca0.1MnO3 particles with size d ≲ 150 nm formed in the composites at the surface of plate-like SrFe12O19 crystallites. The Mossbauer studies showed that the composite contained additional (intermediate) phase La0.9Ca0.1Mn(Fe)O3 that formed at the interface between SrFe12O19 and La0.9Ca0.1MnO3 phases. The intermediate phase concentration increased with the molar content of La0.9Ca0.1MnO3; in this case, the fraction of the surface of SrFe12O19 crystallites coated with La0.9Ca0.1MnO3 increased, which led to the increase in the total area of the interface surface and the intermediate phase concentration.

Thermochemistry of perovskites in the lanthanum–strontium–manganese–iron oxide system

The enthalpies of formation from binary oxides of perovskites (ABO3) based on lanthanum strontium manganite La(Sr)MnO3 (LSM) and lanthanum strontium ferrite La(Sr)FeO3 (LSF) and mixed lanthanum strontium manganite ferrite La(Sr)Mn(Fe)O3 (LSMF) were measured by high temperature oxide melt solution calorimetry. Using iodometric titration, the oxygen content was derived. The perovskites with A-site cation deficiency have greater oxygen deficiency than the corresponding A-site stoichiometric series. Stability of LSMF decreases with increasing iron content. Increasing oxygen deficiency clearly destabilizes the perovskites. The results suggest an enthalpy of oxygen incorporation that is approximately independent of composition.

Mössbauer spectroscopy studies of phase evolution in SrFe12O19/La0.5Ca0.5MnO3 composites

A composite system composed of SrFe12O19 (SFO) and La0.5Ca0.5MnO3 (LCMO) was prepared by a two-stage sol–gel/hydrothermal synthesis technique. Starting conditions were varied to obtain products with 1:1 and 1:2M ratios of SFO:LCMO. The morphology and composition of the composites were characterized by SEM and room-temperature Mössbauer spectroscopy, revealing the growth of nanocrystalline La0.5Ca0.5MnO3 particles (d⩽150nm) on the surface of SrFe12O19 platelets. Mössbauer spectra not only confirm the presence of well-formed M-type hexagonal ferrite in the composite materials, but also demonstrate the formation of a new, intermediate phase La0.5Ca0.5Mn(Fe)O3 at the interface between SFO and LCMO. The signature of the intermediate Fe-containing phase increases with the starting molar content of La0.5Ca0.5MnO3, as a greater fraction of the SrFe12O19 surface is covered by La0.5Ca0.5MnO3, increasing the total interfacial area. The trends in coercivity in the series of samples between 10K and 300K are reported and discussed in terms of sample morphology.

Intrinsic and extrinsic transport properties of Pr 0.67Ba 0.33MnO 3:Ag 2O composites

We have studied the electrical resistivity, magnetoresistance (MR), and specific heat of (1 − x) Pr 0.67Ba 0.33MnO 3: xAg 2O ( x = 0–30 mol% Ag 2O) composite manganites. Two insulator–metal-like transitions ( T P1 ∼ 194 K and T P2 ∼ 160 K) are observed in the electrical resistivity behaviour of the pristine material Pr 0.67Ba 0.33Mn O3 (PBMO). With Ag 2O addition, T P1 becomes sharper whereas T P2 disappears beyond 25 mol% Ag 2O addition. Electrical resistivity also decreases in the composites in the whole temperature range of measurement. Intrinsic MR (due to grain) gets enhanced from 22% for the pure sample to ∼40% for 30% Ag 2O sample with 0.6 T field. Extrinsic MR (due to grain boundary), however, is found to decrease with Ag 2O addition. Peak MR enhances in composite at the same temperature and at low temperature, beyond the peak, it is almost constant in a large temperature window. Anomaly observed in the specific heat ( C P) near the high temperature insulator–metal transition temperature for various samples signifies the onset of magnetic ordering. Also C P vs T trend is similar in all the samples indicating that Ag 2O addition does not produce any magnetic inhomogeneity.

Growth and characterization of large La1‐xPbxMnO3+δ (x=0.32–0.35) crystals

AbstractLarge crystals of La0.63Pb0.37Mn O3+δ with small La(Pb)‐ deficiency of about 0.005‐0.01 at.% were grown by high temperature solution growth method. The structure of the grown crystals was determined as rhombohedral with R‐3 space group by single‐crystal X‐ray diffractometry. The surface morphology of the crystals and the exact chemical composition was examined by scanning electron microscopy and energy dispersive X‐ray analysis methods, respectively. The IR‐transmission spectrum reveals the presence of Mn3+O6‐ and Mn4+O6‐ octahedra in the lattice of La0.63Pb0.37Mn O3+δ crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Non-uniform behavior of La0.7Sr0.3Co1−Mn O3 (y=0.3 and 0.5) compounds

Abstract La 0.7 Sr 0.3 Co 1− y Mn y O 3 compounds ( y =0.3 and 0.5) have been studied by M ( H ), χ ac ( T ) measurements. As for y =0.3, analyses of the high-field portion of the M ( H ) curves indicate the coexistence of a ferromagnetic and a paramagnetic phase. These results indicate that the system is non-uniform, consisting of small isolated ferromagnetic regions in a non-ferromagnetic matrix. Anomalous M ( H ) curves and a frequency-dependent χ ac ( T ) appear at a temperature below 40 K, which signals a low-temperature glassy magnetic phase.

Nonlinear-optical properties of thin La0.7Ca0.3Mn O3 films and dynamics of photoinduced phase transition

Strong optical second-harmonic was observed in a centrosymmetric LCMO thin films in ferromagnetic phase and assigned a s magnetization-induced effect. B y n on-linearopticalexperiment, magnetization is shown to be sensitivefor laser illumination. A threshold of photoinduced demagnetisation depends on the films structure: it isdrastically decreases in the presence of grain boundaries. For steady state conditions, the SHG field is described bypower law with critical exponent 2β=0.64±0.05. Abovethe threshold a complicated dynamics of photoinduceddemagnetization is observed, which is modeled byphotoinduced modification of electron phase separation.

Colossal magnetoresistance effect in the perovskite-type La0.9Sb 0.1MnO3 material

The colossal magnetoresistance oxide compound La0.9Sb0.1Mn O3 has been prepared by solid-state reaction method.The electrical transport and magnetic properties have been measured by superconducting quantum interference device magnetometer.The valence state of Sb is confirmed to be +5 through x-ray photoelectron spectroscopy,so this compound is an electron-doped colossal magnetoresistance material.

Crystal structure of [Mn2(III)(salpa)2Cl2(H2O)2] (H2salpa = 1-(salicylaldeneamino)-3-hydroxypropane)

The manganese complex, (Mn2(III)(salpa)2Cl2(H2O)2], has been prepared and its structure determined using x-ray crystallography. The dimer is a di-μ2-alkoxo complex which is a six-coordinate manganese dimer with unsupported alkoxide bridges and a rare example of a chloride- and water-containing manganese dimer. The complex crystallizes in the monoclinic space group P21/c with a = 9.315(5), b = 11.130(4), c = 11.637(5) A, β = 104.33(3)°, V = 1169.0(9) A3, and Z = 2. The structure comprises discrete binuclear clusters in which the metal atoms are bridged by two alkoxo oxygens of the salpa2− ligands. The Mn—O and Mn—N distances are in good agreement with those found for other manganese(III) Schiff base complexes. The Mn—Cl and Mn—O3 distances are 2.585(2) and 2.371(2) A, respectively, and the Mn ··· Mn distance is 3.001(1) A. In the crystal, there are two types of hydrogen bonding between the H2O molecule and the Cl atom with Cl ··· H(H2O) distance of 2.33(6) (intramolecule: −1 + x, y, −1 + z) and 2.68(6) A (intermolecule: −1 + x, 0.5−y, −0.5 + z).