Mn Composition Research Articles

Synthesis of Fe-Si-B-Mn-based nanocrystalline magnetic alloys with large coercivity by high energy ball milling

Alloys of Fe-Si-B with varying compositions of Mn were prepared using high energy planetary ball mill for maximum duration of 120 h. X-ray diffraction (XRD) analysis suggests that Si gets mostly dissolved into Fe after 80 h of milling for all compositions. The residual Si was found to form an intermetallic Fe3Si. The dissolution was further confirmed from the field emission scanning electron microscopy/energy dispersive X-ray analysis (FE-SEM/EDX). With increased milling time, the lattice parameter and lattice strain are found to increase. However, the crystallite size decreases from micrometer (75–95 μm) to nanometer (10–20 nm). Mössbauer spectra analysis suggests the presence of essentially ferromagnetic phases with small percentage of super paramagnetic phase in the system. The saturation magnetization (M s), remanance (M r) and coercivity (H c) values for Fe-0Mn sample after 120 h of milling were 96.4 Am2/kg, 11.5 Am2/kg and 12.42 k Am−1, respectively. However, for Fe-10Mn-5Cu sample the M s, H c and M r values were found to be 101.9 Am2/kg, 10.98 kA/m and 12.4 Am2/kg, respectively. The higher value of magnetization could be attributed to the favourable coupling between Mn and Cu.

First-principles investigations of Mn doped zinc-blende ZnO based magnetic semiconductors: Materials for spintronic applications

ZnO based magnetic semiconductors are intensively investigated because of showing strong potential as base materials for spintronic devices. In this study, full potential linearized augmented plane-wave plus local orbitals FP-L(APW+lo) scheme of computation is used to explore the structural, electronic and magnetic properties of Manganese-doped ZnO based magnetic semiconductors in zinc-blende (ZB) phase. For comprehensive understanding of Mn-doping effect on ZnO, several compositions of Mn:ZnO for 12.5%, 25%, 37.5%, 50%, 62.5%, 75% and 87.5% of Mn concentration are investigated. Our obtained results show a successful induction of the magnetic moment (MM) by Mn-doping into the ZnO matrix, without any geometrical deformation. However a marginal increase in the value of lattice constants is found up to 25% concentration of Mn for this system and for above compositions, it tends to decrease revealing the formation of secondary phases. It is also found that Mn:ZnO system favors ferromagnetic coupling for 12.5% and 25% of Mn contents that has been switched to anti-ferromagnetic coupling for higher Mn contents. The spin polarized electronic structure of Mn:ZnO system was calculated within the generalized gradient approximation (GGA). In addition, the Hubbard parameter was also employed to improve the electronic band structure calculations. The calculations performed at GGA+U level related to electronic band structures show zero energy gap for majority spin carriers, whereas a considerable energy gap is noted for minority spin carriers. This distinguished response of Mn:ZnO system to majority and minority spin carriers, in terms of resistivity and conductivity, highlights its importance for diverse applications as based material in spintronic devices like spin dependent transports, currents and other spin based electronic applications.

High-field magnetization study of spin-chain compounds Ca3Co2−xMnxO6

High-field magnetization measurements of spin-chain compounds Ca3Co2−xMnxO6 reveal the presence of two metamagnetic transitions within the Mn composition range of x=1.0–0.8. These transitions are associated with spin-configuration changes from zero-field ↑↑↓↓ to ↑↑↓↑, and finally to ↑↑↑↑ along the Cotrig–(Co/Mn)oct–Cotrig–(Co/Mn)oct spin chain. For x=0.6–0.3, however, the magnetization curve presents a single metamagnetic transition, which can be understood as a ↑↓↑↑ to ↑↑↑↑ transition. The zero-field ↑↓↑↑ structure is further supported by the results of total energy calculation of x=0.5.

Preparation of La0.67Ca0.33MnO3:Ag x polycrystalline by sol–gel method

La0.67Ca0.33MnO3:mol%Ag x (LCMO:Ag x , x = 0, 0.04, 0.08, 0.10 and 0.20) ceramics were prepared by sol–gel method. The X-ray diffraction studies of the LCMO:Ag x samples confirm the pure phase of the LCMO composites with Pbnm space group. With the increase of Ag doping from x = 0 to 0.20, the normalized resistivity (ρ/ρ 300K ) of the samples around the metal–insulator transition temperature (T p ) reduced in sequence. Both T p and the peak of temperature coefficient of resistance (T k ) improved 5–8 K. Energy dispersive X-ray spectroscopy analysis showed that the composition of La, Ca and Mn of the obtained LCMO composites was in accordance with the composition of the precursor. The results indicated that the improvement of grain boundaries and crystallization were responsible for the enhancements of ρ, T p and T k of LCMO:Ag x composites. The fitted curves of electrical resistivity for LCMO:Ag x composites indicated that the mechanisms of grain/domain boundary, electron–electron and magnon scattering and adiabatic small polaron hopping are proposed to explain the phase transition of ferro-magnetic metallic region (T < T p ) and the para-magnetic insulating region (T > T p ), respectively.

Composition dependent magnetism in novel triple perovskite Sr3MFeMoO9 (M=Mn, Co, Ni)

Triple perovskite Sr3MFeMoO9 (M=Mn, Co, Ni) ceramics have been prepared under flowing N2 steam. All compositions are single phase and have B-site cation ordering. However, the composition with M=Co shows denser microstructures with smaller grains, the average grain sizes are 700, 500 and 650nm for M=Mn, Co, and Ni, respectively. The chemical states of the surface and interior Mn, Co, Ni, Fe, and Mo cations are analyzed carefully. Both the magnetization-magnetic field curves and magnetization–temperature curves confirm that all compositions show antiferromagnetic behaviors. The Néel temperature of M=Mn and Ni compositions are determined to be 24.4 and 49.5K, respectively. However, M=Co composition shows two magnetic transition temperatures at 70.9 and 180.7K, which is possibly attributed to that the Co cations have intermediate spin-state (3d6, S=1) and high spin states (3d6, S=2). Furthermore, the compositions show semiconductor-like behaviors and neglectable magnetoresistance in whole measuring temperature range. Our results may be helpful for designing novel magnetic materials and for understanding magnetic couplings in triple perovskites.

Metallic Element Composition of Particulate Matter During Day and Night Sampling at a Traffic Site

Day and night period sampling programs were carried out using a versatile air pollutant system to collect fine particulate matter (PM2.5) and coarse particulate matter (PM2.5–10) simultaneously at a traffic junction that is only 60 m from HungKuang University located in Central Taiwan. Therefore, HungKuang University is regarded as the traffic sampling site in this study. Similar measurements were carried out in a previous 2013 study by Fang and colleagues during October 2012 to November 2012. Determination of metallic element composition of fine and coarse particulates collected during the day and the night was accomplished with inductively coupled plasma atomic emission spectrometry (ICP-AES). The results indicated that there were no significant differences in composition of metallic elements Zn, Cu, Cr, Mn, Fe, Pb, and Cd in either coarse or fine particles for both day and night sampling periods. The statistical results indicated no significant differences for metallic elements in the PM2.5–10 particulates for day and night sampling periods. Also, no significant differences were noted for metallic elements in the PM2.5 particulates for day and night sampling periods at this traffic sampling site. The proposed reason is the limited sampling period employed in this study. Another potential reason is the presence of traffic that runs heavily both day and night being a major contributor to the ambient air metallic pollutants in this region.

XAFS studies of diluted magnetic semiconductor Mn-doped ZnSnAs2thin films on InP substrates

Mn-doped ZnSnAs2 (ZnSnAs2 :Mn) thin films with 5.0 and 6.5% Mn composition were epitaxially grown by molecular beam epitaxy on InP (001) substrates. These films had a Curie temperature of 334 K, corresponding to room-temperature ferromagnetism. The local structures around Mn atoms in ZnSnAs2 :Mn were studied by analysis of the X-ray absorption fine-structure spectra. It was found that the Mn atoms substitute into Zn or Sn cation sites, and the Mn‒As bond length is 2.50 A, which is slightly smaller than the value of 2.53 A in a sphalerite (zinc-blende) ZnSnAs2 bulk crystal. The Mn‒As bond length in ZnSnAs2 :Mn is consistent with the value obtained from GaMnAs, and has a smaller value than that obtained from the zinc-blend MnAs thin films grown on a InP substrate.

An extremely stable MnO2 anode incorporated with 3D porous graphene-like networks for lithium-ion batteries

A rational design of MnO2/3D porous graphene-like (PG) (denoted as 3D PG–Mn) composites and their fabrication via a simple and cost-effective redox process have been achieved for the first time. The 3D PG can provide a highly conductive structure in conjunction with a large surface area to support good contact between the MnO2 nanoparticles and effectively enhance the mechanical strength of the composite during volume changes as well as suppress the aggregation of MnO2 nanoparticles during Li ion insertion/extraction. As a result, the 3D PG–Mn composite with a content of 62.7 wt% MnO2 shows a highly stable capacity of up to 836 mA h g−1 after 200 cycles at a current density of 100 mA g−1 and reversible high rate charge–discharge performance. Such a highly stable 3D PG–Mn composite can be produced on a large-scale and might have even wider applications as an anode material in lithium-ion batteries.

Effect of annealing on the magnetic anisotropy of GaMnAs film with low Mn concentration

The effect of annealing on the magnetic anisotropy of a GaMnAs film with a low Mn composition of 2% has been investigated. Hall measurements have been performed with an external field applied in- and out-of-plane. In as-grown samples, the behavior of the Hall resistance indicates that the out-of-plane magnetic anisotropy dominates over the in-plane anisotropy. The vertical anisotropy, however, gradually decreased with increasing annealing temperatures and changed to in-plane dominant anisotropy in the film annealed at 300 °C. Furthermore, it was found that the direction of the uniaxial anisotropy in the domain with the in-plane easy axes, changed from the [110] direction in as-grown film to the [11¯0] direction in the annealed film. This revealed that annealing altered the magnetic anisotropy of the GaMnAs film between out-of-plane and in-plane directions as well as within the film plane.

Microwave absorbance properties of zirconium–manganese substituted cobalt nanoferrite as electromagnetic (EM) wave absorbers

Nanocrystalline Zr–Mn (x) substituted Co ferrite having chemical formula CoFe2−2xZrxMnxO4 (x=0.1–0.4) was prepared by co-precipitation technique. Combining properties such as structural, electrical, magnetic and reflection loss characteristics. Crystal structure and surface morphology of the calcined samples were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). By using two point probe homemade resistivity apparatus to find resistivity of the sample. Electromagnetic (EM) properties are measured through RF impedance/materials analyzer over 1MHz–3GHz. The room-temperature dielectric measurements show dispersion behavior with increasing frequency from 100Hz to 3MHz. Magnetic properties confirmed relatively strong dependence of saturation magnetization on Zr–Mn composition. Curie temperature is also found to decrease linearly with addition of Zr–Mn. Furthermore, comprehensive analysis of microwave reflection loss (RL) is carried out as a function of substitution, frequency, and thickness. Composition accompanying maximum microwave absorption is suggested.

Heavy Metal Content of Total Suspended Air Particles in the Heavily Industrialized Town of Gebze, Turkey

Air pollution is a serious environmental problem in industrialized towns, where a significant portion of the residents live in close proximity to factories and major highways with high traffic load. In this study, the ambient air quality in Gebze, an industrial region with an area of 438 km(2) and a population of 300,000, was characterized in terms for total suspended particulate matter and its composition of trace elements, i.e. Cd, Cr, Cu, Fe, Mn, Ni and Pb. Samples were collected using high volume samplers from March to June 2009 at two sites during the day and the night. A significantly higher Cu concentrations during night suggested that Cu emissions were the result of a local source. The known air toxics, Cd and Ni, had average concentrations (34 and 43 ng/m(3), respectively) higher than proposed by the European Union's ambient air quality standards. These results highlight the potential health risks for the local population.

Variation in the structural and magnetic properties of heterovalent Mn2+–Si4+ substituted MnCrFeO nanoparticles

We have synthesized heterovalent Mn2+–Si4+ substituted MnCrFeO nanoparticles with a nominal composition Mn1+xSixCrFe1−2xO4 (x = 0.0–0.3) via sol–gel auto-combustion method. X-ray diffractometer, transmission electron microscopy, magnetization measurements were used to study the effects of Mn2+–Si4+ heterovalent ions on the structural and magnetic properties of MnCrFeO. As a result, it was found that the Mn2+–Si4+ ions affect the crystalline structures and magnetic properties of MnCrFeO. X-ray diffraction pattern showed that the samples have the single phase cubic spinel structure of which the lattice constant slightly increased upon Mn2+–Si4+ substitution. The mean crystallite size of the samples was in the range of 21–27 nm as deduced from the XRD line broadening. Cation distribution was estimated using XRD data and it shows that Mn2+ and Si4+ ions prefer tetrahedral A-site. Magnetic measurement shows that saturation magnetization and magneton number decreased with Mn2+–Si4+ substitution with the formation of a collinear spin arrangement.

Microstructure and characteristics of interpenetrating β-TCP/Mg–Zn–Mn composite fabricated by suction casting

A novel interpenetrating β-TCP/Mg–Zn–Mn composite was fabricated by infiltrating Mg–Zn–Mn alloy into porous β-TCP using suction casting technique. The microstructure, mechanical property and corrosion behaviors of the composite have been evaluated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical testing, electrochemical and immersion test. It was shown that the composite had a compact structure and the interfacial bonding between Mg–Zn–Mn alloy and β-TCP scaffold was very well. The composite had an ultimate compressive strength of 140±20MPa, which is near with the natural bone (2–180MPa) and about 1000-fold higher than that of the original porous β-TCP scaffold, and it still retained about two fifths of the strength of the bulk Mg–Zn–Mn alloy. The electrochemical and immersion tests indicated that the corrosion resistance of the composite was better than that of the Mg–Zn–Mn matrix alloy, and the corrosion products on the composite surface were mainly Mg(OH)2, Ca3(PO4)2 and HA.

Electrical and magnetic properties of Al3+ substituted Mn–Ni–Zn nanoferrites

Nanostructured Mn–Ni–Zn ferrites with composition Mn0.1Ni0.6Zn0.3AlxFe(2−x)O4 (where x = 0.05, 0.1, 0.15, 0.2) have been prepared by sol–gel method. The structural data obtained by X-ray diffraction (XRD) of all Mn–Ni–Zn nanoferrites confirmed the spinel structure. The XRD data was used to calculate the lattice parameter and grain size. The morphology of nanoferrites was studied using scanning electron microscopy. The elemental composition (atomic percentage) was determined with the help of energy dispersive X-ray analyser. The dielectric permeability, AC and DC resistivity for all compositions were measured and discussed. The highest resistivity was measured for the sample with concentration x = 0.1. Vibrating sample magnetometry was used to study the magnetic properties of nanoferrites. High saturation magnetization of value 38.7 emu/g, coercivity 7 Oe and highest initial permeability 83.7 are measured for the sample consisting x = 0.05 Al concentration. These nanoferrites have various applications in core materials and in electronic device technology.

Structural, magnetic and transport properties of magnetoelectric composites

Magnetoelectric composites of nominal chemical compositions (y)Mn0.45Ni0.05Zn0.50Fe2O4+(1−y)BaZr0.52Ti0.48O3 (where y varies from 0 to 1.0 in steps of 0.20) were prepared by the standard solid state reaction technique. The samples were sintered at various temperatures. X-ray diffraction patterns confirm the presence of the constituent phases. The initial permeability increases with increasing ferrite content and also with increasing sintering temperature. However, there is a slight decrease in initial permeability value for samples sintered above 1573K. The dielectric dispersion is observed at lower frequencies (<103Hz) due to interfacial polarization. The dielectric constant is almost independent at high frequencies (>104Hz) for a particular composition because of the inability of electric dipoles to follow the fast variation of the alternating applied electric field. The ac electrical conductivity increases with increasing frequency, suggesting that the conduction is due to small polaron hopping. The increase in dielectric constant and dielectric loss corresponds to the increase in ac electric conductivity with increasing sintering temperature up to 1573K. The magnetoelectric voltage coefficient of the composites decreases with increasing ferrite content and dc magnetic field.

Carbon-isotope record and palaeoenvironmental changes during the early Toarcian oceanic anoxic event in shallow-marine carbonates of the Adriatic Carbonate Platform in Croatia

AbstractGeochemical (δ13C, δ18O and Mn) compositions of Lower Jurassic shallow-water carbonates cropping out in Croatia were analyzed to elucidate the impact of the early Toarcian oceanic anoxic event (T-OAE) on the Adriatic Carbonate Platform (AdCP). The bulk-rock carbon-isotope records through the studied sections (Velebit-A, Velebit-B and Gornje Jelenje) are characterized by two significant excursions: (i) an initial positive trend interrupted by a pronounced negative shift (c. 2.5‰) that is followed by (ii) an increasing trend of positive values (up to 4.5‰). A comparison with δ13C trends obtained from well-calibrated sections from other localities in Europe shows that the overall character of the early Toarcian negative excursion is clearly reproduced in the curves derived from Croatian shallow-water deposits, which helps to date the sequences and reinforces the global character of the carbon-cycle perturbation. Lower Jurassic sedimentary successions in the studied area show a gradual deepening trend corresponding to deposition of the Toarcian spotted limestones. Assuming that the distinctive negative excursion in the carbon-isotope curves is synchronous across the AdCP, the contact between the spotted limestones and the underlying beds rich in lithiotid bivalves appears to be diachronous within the study area. The Mn record through the Croatian Velebit-A section and, in particular, the rise in concentration (up to 100 ppm) coinciding with the beginning of the δ13Ccarbpositive shift, reflects a change in the redox conditions in seawater that allowed diagenetic incorporation of reduced manganese into the calcite structure of the carbonate sediment during the onset of the T-OAE.

Elasticity of franklinite and trends for transition-metal oxide spinels

The pressure dependence of single-crystal elastic moduli of a natural Mn-rich franklinite, (Mn 0.40 Fe 2+ 0.16 Zn 0.37 Mg 0.03 )(Fe 3+ 1.94 Al 0.08 )O 4 , has been determined by GHz-ultrasonic interferometry in a diamond-anvil cell to 9.8 GPa. The room-pressure elastic constants of franklinite are C 11 = 244(3) GPa, C 12 = 142(4) GPa, and C 44 = 77(2) GPa. Linear pressure derivatives of C 11 and C 12 are 4.3(3) and 3.8(3), respectively, whereas the C 44 modulus exhibits softening, fitted in the P ≤ 10 GPa pressure range to C 44 = 77(2) + 0.29(2) P – 0.018(2) P 2 GPa. The average of Hashin-Shtrikman bounds on the adiabatic bulk modulus ( K S0 ) of franklinite is 175(3) GPa, with pressure derivative K S ′ = 4.3(3), and the shear modulus G 0 = 66(2) GPa with G ′ = 0.09(3). The isothermal compressibility of franklinite was determined from a separate high-pressure, single-crystal X-ray diffraction experiment to 7.8 GPa, yielding K T0 = 173.5(7) GPa fitted with a fixed pressure derivative of K T ′ = 4. When K ′ is fixed to the ultrasonic value of 4.3, we obtain K T0 = 172.2(7) GPa. In contrast to iron-free gahnite (ZnAl 2 O 4 ), franklinite exhibits pressure-induced mode softening of C 44 similar to magnetite (Fe 3 O 4 ). Between end-member compositions ZnFe 2 O 4 (franklinite) and MnFe 2 O 4 (jacobsite), the bulk modulus decreases linearly with increasing %Mn, however we observe non-linear behavior in other elastic moduli, especially C 44 , which displays a pronounced negative anomaly for the mid-range Mn composition. Applying Birch’s law to AB 2 O 4 -type spinels reveals that oxide spinels containing transition metals on both A and B sites follow a distinct trend from other spinels.

Te vapor annealing of indium-doped CdMnTe crystals

Thermal annealing in Te vapor atmosphere was adopted to improve the properties of indium-doped Cd1−xMnxTe (x = 0.2, CdMnTe) wafers grown by the vertical Bridgman method. The wafers before and after annealing were characterized by measuring the Te inclusions, etch pit density (EPD), Mn composition, resistivity, and impurity. IR transmission microscopy and EPD measurements revealed that the densities of Te inclusions reduced from (5–9) × 104 cm−3 to (2–4) × 104 cm−3 and EPD from 105 cm−2 to 104 cm−2 after annealing. NIR transmission spectroscopy showed that the Mn composition increased by 0.002–0.005 mole fractions during the annealing. The resistivity of the wafers improved from (2.0–4.5) × 108 Ω·cm to (1.7–3.8) × 109 Ω·cm, which suggested that the deep-level donor of Te antisites was successfully introduced after annealing. Inductively coupled plasma-mass spectrometry (ICP-MS) revealed that the concentrations of impurities in the wafer decreased, which indicated the purifying effects of Te vapor annealing on the wafers. All the results demonstrate that the Te vapor annealing of the indium-doped CdMnTe crystal has positive effects on the crystallinity, resistivity and purity of CdMnTe wafers.

Characterization of Ru–Mn composites for ULSI interconnects

In this study, PVD Ru–Mn composites were investigated in terms of major concerns that arise with the introduction of a new type of barrier. First, the Cu diffusion barrier performance after annealing at 600°C and under subsequent BTS of +2MV/cm, 250°C was investigated on SiO2, and after 350°C annealing on low-k dielectrics. Ru–Mn films proved to serve as outstanding Cu diffusion barrier over a wide range of Mn content. Second, the origin of the barrier performance was investigated using TEM, EELS and XPS depth profiling techniques, revealing the stuffing of grain boundaries as barrier mechanism. Third, Cu plating on damascene wafers applying a Ru–Mn seed layer was tested, and also the Cu adhesion thereon, resulting in a complete feature fill and excellent Cu wetting behavior. Fourth, the blocking of oxygen diffusion was examined, leading to a performance comparable to PVD TaN. Finally, the Mn content inside Ru was reduced down to 1at.% without compromising the superior material properties.

Magnetic structure of La2O3FeMnSe2: neutron diffraction and physical property measurements

We report on the characterization of the mixed layered lanthanum iron manganese oxyselenide La2O3FeMnSe2, where Fe and Mn share the same crystallographic position. The susceptibility data show a magnetic transition temperature of 76 K and a strong difference between field cooled and zero field cooled (ZFC) data at low fields. While the ZFC magnetization curve exhibits negative values below about 45 K, hysteresis measurement reveals, after an initial negative magnetic moment, a hysteresis loop typical for ferromagnetic material, pointing to competing ferromagnetic and antiferromagnetic interactions. Resistivity and dielectric permittivity measurements indicate that La2O3FeMnSe2 is a semiconductor. We performed x-ray diffraction at 295 K and neutron diffraction at 90 and 1.7 K. The nuclear and magnetic structure was refined in the space group I4/mmm with a = 4.11031 (3) Å and c = 18.7613 (2) Å at 295 K. We did not detect a structural distortion and the Fe and Mn atoms were randomly distributed. The magnetic order was found to be antiferromagnetic, with a propagation vector q = (0,0,0) and magnetic moments of 3.44 (5) μB per Fe/Mn atom aligned within the a–b plane. This magnetic order is different with respect to the pure Fe or Mn compositions reported in other studies.