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The heating characteristics of citrate-coated magnetite nanoclusters in a magnetic inductive system were analyzed with several methods, such as the numerical initial slope method, a fourth-degree polynomial, a single Box-Lucas equation, a sum of two and three Box-Lucas equations, the corrected slope method and its extension. The Box-Lucas equation was modified by considering a half-rate heating constant (λ1/2) rather than the traditional heating-rate constant (λ), which is usually presented in the literature. The nanoclusters, produced by the precipitation method were characterized with high resolution transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy, thermogravimetric analysis and Fourier transform infrared spectrometry. High resolution transmission electron microscopy showed the nanoclusters of the synthesized magnetic particles. According to the X-ray diffraction data, these nanoclusters had average particle sizes ranging from 20 to 31 nm and comprised magnetite. Mössbauer spectroscopy showed the characteristic double magnetic pattern associated with the iron ions located at the A and B sites of the inverse spinel crystal structure for magnetite. Infrared peaks such as those at 1629 cm−1 and 564 cm−1 for the citrate-coated magnetite nanoclusters, suggested that citrate ions were indeed attached to the particle surfaces. Additionally, a thermogravimetric analysis showed that from 4.6 to 10.9 wt% citrate ions were attached to the particle surfaces. Both the modified Box-Lucas equation and the extension of the corrected slope method provided consistent results and greatly simplified estimation of the specific absorption rate of the magnetite nanoclusters used in the magnetic fluid hyperthermia studies. [ABSTRACT FROM AUTHOR]

A series of La3+ ion doped magnesium nickel ferrites, Mg 0.5 Ni 0.5 Fe 2-x La x O 4 (0 ≤ x ≤ 0.1) having a cubic spinel structure were prepared by the co-precipitation method. Various characterization techniques, including X-ray diffractometer (XRD), high resolution transmission electron microscopy (HR-TEM), electron spin resonance (ESR) and vibrating sample magnetometer (VSM) were used to investigate structural and magnetic properties. The average crystallite size decreases and lattice parameter increases with La3+ ion doping and lie in the range of 12–7 nm and 8.347–8.361 Å respectively. Analysis of ESR spectra reveals that, g-value with La3+ ion addition decreases from 2.57 to 2.12. The saturation magnetization and the coercivity decrease with increasing rare-earth content. Magnetic-hysteresis (M − H) loop shifts from a ferromagnetic to a superparamagnetic nature with La3+ ion addition. The dielectric study was carried out in the frequency range of 1 KHz to 4000 KHz and temperature ranging 30 °C–350 °C using the impedance analyzer. The dielectric constant decreases with increasing frequency and the La3+ ion concentration. The dielectric loss of the sample increases with increasing temperature. The magnetic properties of the synthesized nanoparticles make them a potential material for stable ferrofluid application and the low tangent loss value makes these material a potential candidate for frequency-based applications. [ABSTRACT FROM AUTHOR]

Different long-chain primary alkylamines such as octylamine, dodecylamine, tetradecylamine, hexadecylamine or octadecylamine were used to stabilize Ni-NiO nanoparticles (metal:stabilizer ratio of 1:10) by an organometallic method in organic medium to evaluate their effect on the microstructural and magnetic properties. The Ni-NiO stabilized nanoparticles were characterized by Fourier transformed infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), conventional transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and dynamic light scattering (DLS). The results indicated an adequate stabilization of Ni nanoparticles with the different primary alkylamines. The semi-quantitative analysis suggests that Ni surface composition is a combination of the metallic state with NiO, NiOOH and NiO, but the chain length modified the content and proportion of these compounds. The highest Ni metallic state (57.2 at. %) was obtained with tetradecylamine as stabilizer. The morphology of the samples is similar to a core–shell semi-spherical, but the particle size tends to reduce with the alkyl chain length of primary amines from 20 to 8 nm. The saturation magnetization (Ms) showed important variations depending on the surface composition, for which variable particle size and Ni metallic content were determining factors for the magnetic response. [ABSTRACT FROM AUTHOR]

Lanthanum doped magnesium-zinc spinel ferrite samples were synthesized by the simple co-precipitation method with composition M g 0.5 Z n 0.5 F e 2 − x L a x O 4 (x = 0,0.025,0.05,0.075 a n d 0.1). The synthesized ferrite samples were investigated using by powder X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HR-TEM), electron paramagnetic resonance spectroscopy (EPR) and vibrating sample magnetometer (VSM). The effect of the La3+ ion doping on the crystallite size and lattice parameter of the material has been discussed. The crystallite size for all the samples were found to be in the range of 7–12 nm. The percentage porosity and percentage crystallinity of all the samples were found to be in the range of 49–50% and 80–85% respectively. In the frequency region of 400–600 cm−1 two absorption bands attributed to the T d and O h sites of the spinel ferrite have been observed. FTIR band spectra shift from lower to higher region with La3+ ion doping. Agglomeration of the particles is observed in the FE-SEM and HR-TEM images. Additional impurities except carbon are not present in the sample which is confirmed by EDS analysis. EPR analysis shows a decrease in the g-value from 2.18 to 2.12 for the synthesized samples with La3+ ion doping. The resonance field for synthesized sample shifts to higher magnetic field which may be due to ferromagnetic interaction caused by La3+ ion doping. The maximum spin concentration (1.508 × 1021 spin/g) and the relaxation time (4.132 × 10−11 s−1) was observed for the MZL2 composition. Magnetization curve shows the typical superparamagnetic nature of synthesized samples. The calculated squareness value of the synthesized sample refers to the magnetostatic interaction among particles. The obtained coercive field value is low which makes these materials suitable for ferrofluids and hyperthermia treatment applications. [ABSTRACT FROM AUTHOR]

Nanostructured MFe 2 O 4 (M = Co and Zn) ferrites have been successfully synthesized by hydrothermal method using cetyltrimethylammonium bromide (CTAB) as a surfactant and ammonium hydroxide (NH 4 OH) as a precipitating agent at a moderate temperature (∼160 °C) for 10 h and subsequent calcination of the precursors at 400 and 600 °C. These ferrite materials have been characterized by X-ray diffraction (XRD), BET surface area, scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), thermogravimetric analysis−differential scanning calorimetry (TGA−DSC), Fourier transformed infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The CoFe 2 O 4 is found to have both hexagonal and spherical surface morphologies and for ZnFe 2 O 4 a spherical morphology is obtained at 600 °C. Optical, dielectric, and magnetic properties of these ferrites have been investigated. CoFe 2 O 4 exhibits ferromagnetism at room temperature. In contrast, ZnFe 2 O 4 shows paramagnetism at room temperature. The M s and H c values are observed to increase, respectively, from 74.2 emu g−1 to 78.9 emu g−1 and 1221 Oe to 1411 Oe for CoFe 2 O 4 as the calcination temperature increases from 400 °C to 600 °C. This is related to better crystallinity because of calcination at higher temperature. Dielectric properties of the ferrite materials are also enhanced with the increase in the calcination temperature. [ABSTRACT FROM AUTHOR]

• Hard/soft nanocomposites were prepared by one-pot sol–gel auto-combustion technique. • The composition exhibited a good exchange-coupling. • Strong correlation between the chemical composition and electrodynamic parameters. This work presented the effect of Ho substitution on magnetic and electrodynamic properties of hard-soft SrBaHo x Fe 12-x O 19 @NiFe 2 O 4 (x ≤ 0.06) nanocomposites (H/S Ho → SBFeO@NFO NCs) which were produced through one-pot citrate sol–gel method. The structure and morphology were explored using X-ray diffractometry (XRD) and scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM). By scrutinizing hysteresis curves at temperatures of 300 K (Room temperature, RT) and 10 K, the magnetic characteristics of H/S Ho → SBFeO@NFO (x ≤ 0.06) NCs have been investigated. These materials display smooth, open hysteresis loops at both temperatures, indicating their ferrimagnetic nature and highlighting the presence of exchange-coupling interactions within the nanocomposites. The SQR (squareness ratio) values, below 0.5 at both high and low temperatures, indicate a multi-domain structure in the H/S Ho → SBFeO@NFO (x ≤ 0.06) NCs. Magnetic parameters demonstrate fluctuations with growing Ho content. The introduction of Ho3+ ions notably reduce the coercivity of the undoped H/S Ho → SBFeO@NFO (x ≤ 0.06) NCs. Saturation magnetization (M s) and magnetic moment show similarity between undoped and Ho-doped nanocomposites at all concentrations, except for x = 0.06, where a considerable decrease occurred at both temperatures. Our findings propose that by controlling the concentration of Ho3+ ions, the magnetic properties of H/S Ho → SBFeO@NFO NCs can be precisely adjusted. Electromagnetic properties of the H/S Ho → SBFeO@NFO NCs were investigated in the range 33–50 GHz. Frequency dispersions of the real/imaginary parts of permittivity and permeability were determined from S11 to S21 parameters. RL coefficient demonstrated intensive electromagnetic absorption with average level −16...−23 dB in this frequency range that corresponded to the absorption of the natural media. [ABSTRACT FROM AUTHOR]

Magnetoplumbite barium hexaferrite (BaFe 11.8 Co 0.2 O 19) is synthesised through sol-gel auto-combustion method under two pH conditions of precursor solutions (acidic i.e. pH < 1 and neutral i.e. pH = 7). The XRD analysis followed by Reitveld refinement indicates the formation of phase pure samples in both cases but the barium hexaferrite obtained from acidic precursor solution has smaller crystallite sizes. The Transmission Electron Microscopy (TEM) analysis followed by High Resolution Transmission Electron Microscopy (HRTEM) confirms a lower particle size of ∼20 nm for barium hexaferrite synthesised from acidic pH precursor solution. The shift in Raman peak (520-540 cm−1) by 20 cm−1, represents the whole structural block and further confirms the differences in the distribution of particle sizes due to the method of synthesis. The magnetic studies display a lower coercive field for the samples with smaller particle sizes. This is due to the crystalline size-induced microstrain that controls the magneto-crystalline anisotropy, shape anisotropy and stress anisotropy. The electromagnetic characterisation confirms broader absorption in the range of 8–18 GHz (X -band) with R L ≤ −7 db for the entire range for the samples with smaller particle sizes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn x Fe 2-x Mg 0.5 Ni 0.5 O 4 spinel ferrites were prepared utilizing a flash auto-combustion technique. • XRD confirmed formation of cubic phase spinel ferrite phase with space group Fd-3 m. • FTIR spectra validate the positions of the cations and their vibrational modes. • Optical band gaps Eg of investigated samples were found to decrease from 1.79 eV to1.24 eV. • The magnetic properties demonstrated soft ferrite nature with small hysteresis curve. Mn x Fe 2-x Mg 0.5 Ni 0.5 O 4 spinel ferrite nanoparticles (0.0 ≤ x ≤ 1) were prepared utilizing a flash auto-combustion technique. The as-prepared ferrite nanoparticles have been investigated and characterized using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and Fourier transform infrared analysis (FTIR). The dielectric, optical and magnetic characteristics of the synthesized spinel ferrite samples were investigated using broadband dielectric spectroscopy (BDS), diffuse reflectance spectroscopy (DRS) and vibration sample magnetometers (VSM). The cubic phase spinel ferrite with space group Fd-3m was identified through XRD. X-ray diffraction indicates that the lattice constant increases and the crystallite size declines with increasing Mn concentration. The positions of the cations and their vibrational modes in the crystal structure with oxygen ions are demonstrated through the FTIR spectra. The morphology was examined using HRTEM showed polycrystalline cubic spinel structure with faceted planes. The optical band gap Eg was determined using Kubelka–Munk model where, it decreased from 1.79 eV to1.24 eV as Mn content increases. The replacement of manganese significantly affects the dielectric characteristics of the synthesized spinel ferrites. The real (ε′), imaginary (ε″) parts of dielectric constant and ac conductivity exhibit an increase in their values as manganese substitution (x) increases from 0 to 0.25 mol %, and thereafter decreases. The presence of a relaxation phenomenon in all prepared samples except the undoped sample (Ni 0.5 Mg 0.5 Fe 2 O 4) is shown by the imaginary modulus's (M′′) dependence on frequency. The magnetic properties exhibited soft ferrite nature with small hysteresis curve for all spinel ferrites samples. The magnetic properties of Mn x Fe 2-x Mg 0.5 Ni 0.5 O 4 nanoparticles were measured and analysed, including saturation magnetization (Ms), remanence (Mr), coercivity (Hc), and squareness ratio. (Ms), and (Mr), exhibit an increase in their values as manganese substitution (x) increases from 0 to 0.25 mol %, and thereafter decreases while squareness ratio decreased. The magnetic parameters greatly affected by Mn substitution ratio. [ABSTRACT FROM AUTHOR]

Multiferroic (x)BaTiO3/(1 − x)Li0.5Fe2.5O4 (0.0 ≤ x ≤ 1) perovskite/spinel nanocomposite was synthesized using a modified citrate auto-combustion method. Both BaTiO3 (BTO) and Li0.5Fe2.5O4 (LFO) phases along with their composites were successfully characterized using X-ray diffraction, Fourier transformation infrared spectroscopy, and X-ray absorption fine structure spectroscopy. The nanoscale, morphology, and magnetic properties were imaged and acquired using high resolution transmission electron microscopy, atomic force microscopy, and vibrating sample magnetometer. Synchrotron radiation-based elemental selective XAFS technique was performed around Fe K-edge to obtain the selective and the detailed local structural information of Li0.5Fe2.5O4 nanoparticles (NPs). The main remarkable result in this work is the enhancement in the coercivity (HC) of LFO NPs after compositing with BTO particularly at x = 0.6, and at x = 0.8. Based on the collected results, BTO/LFO nanocomposite can be seen as a good candidate for different technological applications including magnetically modulated piezoelectric, safety rechargeable batteries, and multilayer ceramic capacitor. [ABSTRACT FROM AUTHOR]

[Display omitted] • Facile microwave combustion synthesis of Cu 1-x Co x Fe 2 O 4 (0 ≤ x ≤ 0.5) NPs is reported. • Synthesis of CuFe 2 O 4 at all Co contents is noticed to be monophasic cubic. • The band gap has been enhanced from 2.30 to 2.50 eV on Co doping. • The M s values are found to be improved from 17.40 to 24.80 emu/g with Co doping. • An enhancement in photocatalytic activity of CuFe 2 O 4 NPs was observed with Co doping. Magnetic nanoparticles are found to have tremendous applications towards opto-magnetic-photocatalytic fields. Hence, herein authors make the efforts to prepare CuFe 2 O 4 (CFe) nanoparticles (NPs) with different Co contents Cu 1- x Co x Fe 2 O 4 (0 ≤ x ≤ 0.5) (CCFe NPs) through microwave combustion process for the first time. Mono phasic preparation of CFe NPs at all Co contents was confirmed via structural analysis. The oxidations states of the prepared NPs were carried out via X-ray photoelectron spectroscopy (XPS). The morphological analysis and chemical compositions of the prepared samples were observed by high resolution scanning electron microscopy (HRSEM) with energy dispersive X-ray spectroscopy (EDX) respectively. Kubelka-Munk model was used to estimate energy gap and found between 2.30 and 2.50 eV. The electron and hole pairs recombination rate and presence of defects were studied via Photoluminescence spectra. The saturation magnetization, M S , remanant magnetization, M r and coercivity, H C were obtained to be improved from 17.40 to 24.80 emu/g, 5.18 to 8.73 emu/g & 331.89 to 1698.12 Oe, respectively. A detailed photocatalytic nature of the prepared CFe and CCFe NPs via hazardous RhB dye degrading beneath of irradiation of visible light (λ > 420 nm) was carried out. The possible mechanism of RhB dye degradation along with optimum Co doping in CFe and commanding active species has been discussed. These outcomes reveal that the Co doping play a key role in improving the optical band gap, magnetic and photocatalytic properties of CFe NPs. [ABSTRACT FROM AUTHOR]

Cobalt doped SnO2 nanoparticles were prepared for different molar concentration 2%, 4% & 6% of Co by Chemical co precipitation method. The prepared samples were characterized by X-ray diffraction (XRD), UV-visible absorption spectra, Photoluminescence (PL), High Resolution transmission electron microscopy (HRTEM) and Vibrating sample magnetometer for their Structural, Optical and Magnetic Properties. The doping concentration of Co induces crystal phase, crystallite size, lattice distortion, optical and magnetic properties were investigated. XRD Results showed that Co2+ replaces Sn4+ in the crystal lattice of SnO2, which enhanced the growth of crystallite size and suppressed the transformation from anatase to rutile phase due to lattice distortion produced in SnO2. The UV absorption studies concluded the band gap of Co doped SnO2 nanoparticles decreased from 3.79 eV to 3.62 eV in visible region. PL spectra exhibit only a broad emission peak in the range of 420 nm to 540 nm and excitation is observed at the wavelength of 385 nm. New energy levels are not formed in the band structure to produce new emission due to Co doping and also indicates that the substitution of Co2+ ions for Sn4+ ions without the formation of other additional energy levels. Due to increasing Co concentration in SnO2, the emission energies are decreasing the peak intensities. An efficient method for inducing the ferromagnetic behavior from increasing the Co concentration from 2% to 6 % was known from the magnetization versus magnetic field (M--H) curves at room temperature of the Co doped SnO2 samples. The dominant magnetic interaction between Co ions, and hence, the ferromagnetic behaviour increases for increase in Co2+ doping concentration.Consequently, to achieve the good ferromagnetic character in these materials, the concentration of Co dopant has to be properly optimized. [ABSTRACT FROM AUTHOR]

In this study we investigated the influence of Gd 3 + ions on the structural and magnetic properties of (Nb + Al) co-doped TiO 2 single crystals with nominal composition Ti 0.995 (Nb 0.667 Al 0.333) 0.005 O 2 (TNA) and Ti 0.995 (Nb 0.667 (Al 0.1665 Gd 0.1665)) 0.005 O 2 (TNAGd) grown in an optical traveling floating zone (TFZ) furnace. The crystal structure and phase purity investigated by X-ray diffraction (XRD) and High resolution transmission electron microscopy (HRTEM) images of selected area electron diffraction (SAED) patterns confirmed the rutile crystal nature for both TNA and TNAGd samples. The magnetic properties were studied from 3 to 400 K in magnetic fields up to 60 kOe. ZFC/FC curves revealed paramagnetic behavior for TNA sample, while the presence of Gd 3 + ions in the crystal structure drastically affected the magnetic properties turning to ferromagnetic behavior. The isothermal magnetization, M(H) curves for TNAGd samples were analyzed by the bound magnetic polaron (BMP) model. At the lowest temperature the values of the total moment of BMP's (M 0), spontaneous moment of a single BMP (m s), and the concentration of BMP's (N) were found to be 1.58 emu / cm 3 , 840 μ B , and 3.2 × 10 19 BMP / cm 3 , respectively. The number of Gd 3 + ions per BMP was ~ 113 and 75% of Gd 3 + ions were inside the BMP's and the remaining 25% were outside but diluted in the matrix or interacting antiferromagnetically. [ABSTRACT FROM AUTHOR]

This work reports experimental and computational magnetic phase transition from superconducting-diamagnet to ferromagnet in lanthanum (La)-doped functionalized Nb2C MXene. Co-precipitation method is used to synthesize La-doped Nb2C MXene. Structure and morphology of the compound are studied through x-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and energy dispersion spectroscopy, confirming the successful doping of La while retaining the two-dimensional (2D) structure of MXene. The magnetic properties of doped sample are studied using field-cooled and zero-field-cooled curves as well as from magnetization (M) versus applied magnetic field (H) graphs. Contrary to the superconductivity-like diamagnetic behavior in pristine Nb2C MXene, the La-doped MXene converts the diamagnetism into the ferromagnetic (FM) phases at all temperatures. The ferromagnetism arises due to the pinning of magnetic spins pinned by Lanthanum itself. The computational analysis of pristine Nb2C MXene confirms its diamagnetic behavior and further clarifies the role of La and functional groups (O and F) in the reduction of diamagnetic behavior in La-doped Nb2C MXene while inducing FM nature. This work provides an interesting superconducting-diamagnetic to FM transition with a possibility of its implementation in 2D spintronics. [ABSTRACT FROM AUTHOR]

Lanthanum Strontium Manganite (La1−xSrxMnO3) perovskite nanoparticles are prepared by ultrasonication assisted hydrothermal method with different Sr concentration (x = 0.1, 0.3, 0.5). The structural, magnetic and electrical properties of the prepared samples are studied by powder X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), high-resolution transmission electron microscopy (HRTEM), vibrating sample magnetometry (VSM) and impedance spectroscopy. The Powder XRD and EDX studies confirmed the formation of LaSrMnO3. The powder XRD patterns show that the crystallite size decreases from 27.2 to 19.7 nm as the Sr concentration increases from x = 0.1 to x = 0.5. A shift in peak position towards higher angle indicates the replacement of La ions by Sr ions in the LaMnO3 lattice. Electron microscopic images show that the La1−xSrxMnO3 samples having both spherical and polygon morphology with decreasing particle size as the Sr concentration increases. The selected area electron diffraction (SAED) pattern confirms the polycrystalline nature of the La1−xSrxMnO3(x = 0.5) nanoparticles. The magnetic study indicates that the La1−xSrxMnO3 samples exhibits ferromagnetism at room temperature, which increases with increasing of Sr concentration. Dielectric analysis shows the dielectric constant decreases with the function of frequency and increases with Sr content. With increase in frequency and Sr ions dopant concentration, the AC conductivity of the prepared samples is increased. The Cole–Cole plot shows the different radii of the semicircles exhibit the resistances of La1−xSrxMnO3 samples are highly dependent on the Sr concentration. [ABSTRACT FROM AUTHOR]

We report on detailed study of detonation nanodiamonds (DNDs) whose surface has been chemically modified by copper with the aid of ion exchange in water DND suspension. High resolution transmission electron microscopy, Raman, IR, electron magnetic resonance (EMR), nuclear magnetic resonance (NMR), and superconducting quantum interference device techniques were used for the characterization of DND. Carboxyl groups, appearing on the surface of a nanodiamond particle during its synthesis and purification processes, provide an effective binding of divalent copper ions to the surface. The binding results from the ion exchange between metal cations and protons of surface carboxyl groups in water solutions. IR data evidence the presence of multiple C[Single_Bond]O[Single_Bond]C groups in the dried copper-modified DND product. Both EMR and 13C NMR provide direct evidences of the appearance of isolated Cu2+ ions on the surface of the 5 nm nanodiamond particles. EMR spectra reveal well-pronounced hyperfine structure due to 63,65Cu nuclear spin I=3/2 with the spectral pattern which is typical for mononuclear axially distorted Cu2+ complexes in polycrystals. Using Cu2+ ions as paramagnetic probes two-component model of carbon inherited paramagnetic centers in DND is suggested. Magnetic susceptibility for all samples follows the Curie–Weiss law above 30 K. The concentration of magnetically observable copper ions Cu2+ (spin S=1/2) localized on the nanodiamonds surface increases up to approximately 1.5–3.5 ions per nanoparticle with increasing concentration of copper acetate in starting solutions. [ABSTRACT FROM AUTHOR]

La2/3Ca1/3MnO3 (LCMO) films have been deposited on (110)-oriented SrTiO3 (STO) substrates. X-ray diffraction and high-resolution electron microscopy reveal that the (110) LCMO films are epitaxial and anisotropically in-plane strained, with higher relaxation along the [1–10] direction than along the [001] direction; x-ray absorption spectroscopy data signaled the existence of a single intermediate Mn3+/4+ 3d-state at the film surface. Their magnetic properties are compared to those of (001) LCMO films grown simultaneously on (001) STO substrates It is found that (110) LCMO films present a higher Curie temperature (TC) and a weaker decay of magnetization when approaching TC than their (001) LCMO counterparts. These improved films have been subsequently covered by nanometric STO layers. Conducting atomic-force experiments have shown that STO layers, as thin as 0.8 nm, grown on top of the (110) LCMO electrode, display good insulating properties. We will show that the electric conductance across (110) STO layers, exponentially depending on the barrier thickness, is tunnel-like. The barrier height in STO (110) is found to be similar to that of STO (001). These results show that the (110) LCMO electrodes can be better electrodes than (001) LCMO for magnetic tunnel junctions, and that (110) STO are suitable insulating barriers. [ABSTRACT FROM AUTHOR]

Over the years, a wide range of spectral research has been carried out on various carbon forms to explore deeply their structure-property relationship. The structural stability of carbon allotropies remains to be a challenging endeavor yet to be achieved under extreme conditions, especially under acoustical shocked conditions. From the experimental findings, we report the acoustic shock wave response of the amorphous carbon nanoparticles and the resultant degree of crystalline nature, morphological characteristics and magnetic response. Moreover, analytical techniques such as X-ray diffractometry (XRD), Raman spectrometer, High resolution transmission electron microscopy (HR-TEM) and vibrational sample magnetometer (VSM) have been employed to arrive at the relationships of structure – morphology – magnetic properties under shocked conditions. Interestingly, under shocked conditions (0, 250, 500 and 750 shocks), compelling evidence has been found for the short-range amorphous pockets which turn into spatially short-range ordered graphitic domains within the sphere-shaped amorphous nanoparticles whereby the obtained values of the ratio I D /I G of the samples are 0.94, 0.93, 0.95 and 1.01 for 0, 250, 500 and 750 shocked conditions, respectively. Moreover, the saturation magnetization is found to have reduced in the base of the local atomic ordering and the obtained values are found to be 1, 0.64, 0.41, 0.725 emu/g for 0, 250, 500 and 750 shocked conditions, respectively. The structure-property relationship is to be elaborated in the upcoming sections. [Display omitted] • Shock wave induced amorphous carbon to short-range ordered graphitic domains is reported. • The I D /I G intensity ratio of the samples is 0.94, 0.93, 0.95 and 1.01 for 0, 250, 500 and 750 shocked conditions. • The saturation magnetization values are 1, 0.64, 0.41 and 0.725 for 0, 250, 500 and 750 shocked conditions. • The correlation of the magnetic properties and degree of crystalline nature is discussed. [ABSTRACT FROM AUTHOR]

One dimensional Gd 2 O 3 nanorods with 5% Eu substitution at Gd-site have been synthesized by a simple, inexpensive, hydrothermal process without using any catalyst or template. Structural, spectroscopic, magnetic and magnetocaloric properties of these nanorods are studied. Powder X-ray diffraction data confirm that these samples have cubic structure (Space group Ia-3) at 300 K. High resolution transmission electron microscopy images suggest the average diameter of nanorods to be ~14 nm. However, the rod length is found to vary from about 50 nm to 140 nm. Raman spectrum shows a peak at ~363 cm−1 as expected for the cubic phase of Gd 2 O 3. The 5% Eu substituted Gd 2 O 3 sample remains paramagnetic from 300 K down to 5 K. Using magnetization–field data obtained at various temperatures, isothermal magnetic entropy change (ΔS m) is calculated. The maximum ΔS m value at 6 K for 70 kOe field change is about −30.3 Jkg−1 K−1. This value is quite large compared to that of the pure Gd 2 O 3 nanotube samples. Thus nanostructured Gd 2 O 3 with small rare-earth substitution at Gd-site exhibit appreciable magnetocaloric effect and these nanomaterials may be suitable for low temperature magnetic refrigeration applications. • Eu-doped Gadolinium oxide (Gd 2 O 3) nanorods have been synthesized using a simple surfactant/template/catalyst-free hydrothermal method. • Magnetic and optical properties of 5% Eu-substituted Gd 2 O 3 nanorods are studied. • Surface spin disorder leads to enhanced magnetization and magnetocaloric effect at low temperatures. [ABSTRACT FROM AUTHOR]

We report on the one-step synthesis of vertically aligned multiwalled carbon nanotubes (MWCNTs) filled with Co magnetic nanowires via bias-assisted plasma enhanced chemical vapor deposition (PECVD) method. Co/Pd bilayer, both of nanometric thicknesses, deposited onto 50 nm thick TiSiN serving as a diffusion barrier was used as catalysts for nanotube growth. The process gas was a mixture of acetylene (carbon source) and ammonia. A 6 mbar growth pressure combined with 200 W plasma power permitted to achieve simultaneously the growth, alignment and filling of the carbon nanotubes. The plasma was activated by applying a negative bias between − 500 and − 600 V to the substrate. Structural investigations of 1D cobalt rich nanocrystals confined in vertically aligned carbon nanotubes were carried out by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) to elucidate the growth mechanisms. Statistical analysis was performed on the nanotubes peeled from the forest and dispersed. Spatially resolved electron energy loss spectroscopy (EELS) and energy filtered elemental mapping revealed that the nanotubes are mainly filled with cobalt X-ray photoelectron spectroscopy (XPS) confirmed the presence of Co, Pd, C, N and O, with weak degrees of oxidation of the metallic Co and carbide Co formation. Hysteresis cycles, from vibrating sample magnetometer (VSM) measurements at room temperature, exhibited a ferromagnetic behavior with coercive field H C values well above those usually reported for continuous layers. H C is also observed to be higher when the Co nanoparticles embedded in the CNTs exhibit nail shape than spherical or cylindrical one. This can be explained by a lower mean diameter. This shape aspect influences the nature of the magnetization reversal probably operating through curling process. These results open up the potential for one step growth, alignment and filling of carbon nanotubes with potential applications as spintronic devices. [Display omitted] • One step plasma enhanced CVD growth and filling of carbon nanotubes with cobalt. • Nanotube growth and filling was improved by using Co and Pd bilayer catalyst deposited onto TiSiN diffusion barrier. • Control of filling was performed by varying substrate temperature, applied bias and plasma power. • Confined 1D cobalt rich nanowires network with lengths up to 5 µm and aspect ratio up to 20 was obtained. • Magnetic properties of embedded nanowires are shape dependent and enhanced regarding to catalyst film. [ABSTRACT FROM AUTHOR]

Nanoparticles with various compositions of Fe–Rh have been fabricated by a solution phase chemical method and their magnetic properties characterized. After refining and size selection, the average particle size is about 2–5 nm by high-resolution transmission electron microscopy observation. From x-ray diffraction results, as-deposited FeRh nanopaticles reveal a typical chemically disordered fcc structure which can be transformed into CsCl-type structure through thermal annealing. Under selected annealing conditions, the coercivities, Hc, for FeRh nanoparticles measured at room temperature are increased, compared with that of their as-deposited states. This increasement in Hc is due to the crystallization of CsCl-type structure after annealing. Nanoparticles of Fe36Rh64 and Fe38Rh62 annealed at 600 °C for 6 h show the presence of the magnetic phase transitions, while those of Fe75Rh25 particles did not exhibit such a transition. [ABSTRACT FROM AUTHOR]

In this work, we report on the anisotropic growth of α -Fe 2 O 3 nanoslabs which are produced by co-precipitation method with the addition of sucrose. In our previous work, we have argued that such behavior can be related with the chelating agent. Experiments of X-ray diffraction (XRD), high-resolution transmission electronic microscopy (HRTEM) and magnetic measurements as a function of temperature and an applied magnetic field are used to characterize the samples. The HRTEM image of the sample prepared with 10 mmol/l of sucrose consists of faceted-like nanoslabs while that prepared without sucrose exhibits particles with a non-uniform shape. In this way, we can state that both the HRTEM images and the analysis of the XRD patterns show clearly a preferential growth of the [110] crystallographic direction. To strengthen our supposition, besides T - and field-dependence of magnetization are consistent with a superparamagnetic behavior the fit of the (Zero Field Cooling and Field Cooling) ZFC-FC curve for sample grown with 10 mmol/l of sucrose presents a strong increase of the effective anisotropy constant, K eff , which can be related with the increasing of the shape magnetic anisotropy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co doped Ceria, Ce 1-x Co x O 2 (x = 0.1, 0.2, 0.3 mol %) were synthesized by combustion method at 500 °C. • Structure, morphology and spectroscopic studies of the nanopowders were studied. • Room temperature ferromagnetism was observed in this material. In this investigation, cobalt doped ceria nanopowders, Ce 1-x Co x O 2 (x = 0.1, 0.2 and 0.3mol.%) were synthesized by citrate–nitrate auto-combustion method at 500 °C in an open furnace. The prominent X-ray diffraction pattern peaks corresponding to the crystallographic planes (1 1 1), (2 0 0), (2 2 0), (3 1 1), (2 2 2), (4 0 0) and the cell parameters confirm the cubic fluorite crystal structure of the ceria with the help of powder diffraction standard (JCPDS card No.00-034-0394). The UV–Visible absorption due to the charge transfer of O2− → Ce2+ and other functional groups were studied by UV–Visible and FT-IR spectroscopic analyses. The visible light emission (wavelength of 420 nm and 520 nm are corresponding to the defect levels of the O 2p and Ce 4f bands) due to oxygen and other vacancies were confirmed by photoluminescence spectroscopy. Energy band gap (E g) of the Ce 0.9 Co 0.1 O 2 , Ce 0.8 Co 0.2 O 2 and Ce 0.7 Co 0.3 O 2 was found to be 1.423 eV, 1.375 eV and 1.332 eV, respectively. The porosity, agglomeration, particles size, shape and distribution of the synthesized nanoparticles were analyzed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM). The energy dispersive X-ray spectroscopy (EDX) confirms the presence of constituent elements of Ce 1-x Co x O 2 such as Ce, Co, and O. The existence of weak ferromagnetism and its variation due to cobalt concentration were studied by vibrating sample magnetometry (VSM) at room temperature. [ABSTRACT FROM AUTHOR]

Spinel structured zinc ferrite (ZF) has been green synthesized using microwave-assisted solution combustion method. Toxic free Hibiscus leaves extract was used as a reducing agent in the synthesis process. Rietveld refinement analysis of high-resolution X-ray diffraction (XRD) pattern confirmed that the ZF has cubic spinel structure with the average crystallite size of 10.47 nm. Agglomerated spherical shapes were observed in green synthesized spinel ZF by scanning electron microscope. The estimated average particle size was found to be 11.52 nm by high resolution transmission electron microscopy imaging. The Zn, Fe and O are the main elements present in spinel ZF, analysed from energy dispersion X-ray analysis. Tetrahedral and octahedral lattice sites which are related to Zn–O and Fe–O bonds were identified by Fourier transform infra-red and Raman spectra. The estimated optical energy bandgap of spinel ZF is found to be 2.17 eV using diffuse reflectance spectroscopy. The Vibrating sample magnetometer results showed single domain superparamagnetic nature of spinel ZF at room temperature. In addition, antibacterial properties of spinel ZF were tested using agar dispersion and agar well diffusion methods on gram negative bacteria Escherichia coli DH5α, after 24 h the bacterial growth completely inhibited. [Display omitted] • Spinel zinc ferrite oxide (ZnFe 2 O 4) was successfully green synthesized using Hibiscus leaf extract as a stabilizing agent. • Spinel structure of ZnFe 2 O 4 explained by HR-XRD analysis. • Agglomerated particles are observed in spinel ZnFe 2 O 4. • The estimated optical energy bandgap of green synthesized spinel ZnFe 2 O 4 is 2.17 eV. • The spinel ZnFe 2 O 4 has good antibacterial properties against gram negative E. coli DH5α bacteria. [ABSTRACT FROM AUTHOR]

Undoped and Mn doped SnO2 prepared by co-precipitation method exhibits nanocrystalline nature with prominent peaks along (110), (101), (211), and (310) planes. All the prepared samples are nanocrystalline with crystallite size lying in the range of 4.8-5.6 nm. The prepared SnO2 nanoparticles exhibit single tetragonal crystalline phase. The high resolution transmission electron microscopy images show that the particles are nanocrystalline in nature. The composition of the prepared samples have been analyzed using energy dispersive analysis of X-rays spectra. The photoluminescence spectroscopy shows the recombination of electrons in singly occupied oxygen vacancies with photoexcited holes in the valence band. Broad UV emission at 426 nm is observed in photoluminescence. UV-vis absorption spectral studies showed a peak at 385 nm. Magnetic measurements revealed that all the doped samples exhibit room temperature ferromagnetism, which is identified as an intrinsic characteristic obtained on doping. Pure SnO2 nanoparticles showed diamagnetism, SnO2 with lower Mn content show larger magnetization and with increasing Mn content the retentivity and coercivity are found to decrease. [ABSTRACT FROM AUTHOR]

• Hard-soft SrFe 12 O 19 /(CoEu 0.02 Fe 1.98 O 4) x nanofiber composites were prepared via electrospinning technique. • XRD, SEM and TEM analyses revealed the coexistence of hard and soft phases. • The magnitudes of optical bandgap E g are in the range of 1.56–1.77 eV. • The degree of exchange-coupling between hard and soft phases is well achieved. SrFe 12 O 19 (SFO) nanofibers (NFs), CoEu 0.02 Fe 1.98 O 4 (CEFO) NFs, and hard-soft (H/S) SrFe 12 O 19 (SFO)/(CoEu 0.02 Fe 1.98 O 4) x (CEFO) (x = 1.0, 1.5, 2.0, 2.5) nanofiber composites (NFCs) were produced via electrospinning approach. The X-ray powder diffraction (XRD) patterns for the studied compositions confirmed the coexistence of characteristics peaks of both phases (Sr-M-type hexaferrite and cubic spinel ferrite) without any impurity. The lattice parameters 'a′ and 'c′ for hexagonal SFO and 'a′ for CEFO NFs are fluctuating with increasing the ratio of CEFO NFs. The surface of nanofibers showed fibers having some roughness and bumps. They are consisted of hexagonal particles belong to SFO mixed and fine cubic CEFO NFs. These observations were confirmed by SEM (Scanning electron microscopy) along with EDX (Energy dispersive X-ray) and HR-TEM (High resolution transmission electron microscopy). The fibers showed a non-uniform cross-section with diameter between 33 and 95 nm. Diffuse reflectance spectroscopic (DRS) investigations were performed on SrFe 12 O 19 NFs, on soft CoEu 0.02 Fe 1.98 O 4 NFs, and on H/S (SFO)/(CEFO) (x = 1.0, 1.5, 2.0, 2.5) NFCs. Tauc method provided the estimation of optical bandgap (E g) of each sample. The magnitudes for E g are in the range of 1.56–1.77 eV. The magnetic responses of all samples in external applied magnetic field (M-H) were recorded at ambient temperature (T = 300 K) and low temperature (T = 10 K). Diverse produced nanofiber composites do not display no kinks in the measured M-H curves at both temperatures. Moreover, a single intense peak was clearly observed in the curves of dM/dH vs. H. These results reflected that the degree of exchange-coupling between hard and soft phases is well achieved via the employment of the electrospinning technique. At ambient temperature, it was observed that the magnetization is improving while the coercivity is diminishing with the increase in H/S ratio. On the contrary, at T = 10 K, the rise of CoEu 0.02 Fe 1.98 O 4 content within diverse H/S NFCs provokes a slight decline in magnetization and a great enlargement in coercivity. The plausible reasons for such tendencies were discussed. [ABSTRACT FROM AUTHOR]

We report on the effect of cooling rate on the size-dependent atomic ordering of CoPt nanoparticles using aberration corrected high-resolution transmission electron microscopy. It was found that cooling rate plays a crucial role in promoting atomic ordering during the cooling process after annealing. Nanoparticles of ≈3 nm in diameter show the A1-disordered phase after annealing at 873 K for 1 h followed by rapid cooling (110 K/min), while the L10-ordered phase is obtained when the cooling rate is slow (1.5 K/min). The disordered phase is also obtained by rapid cooling after annealing at 973 K for 1 h. These results unambiguously indicate that the order–disorder transformation temperature is reduced to a temperature at least lower than 873 K for CoPt nanoparticles smaller than 3 nm in diameter. The slow cooling process promotes the atomic ordering, which resulted in an enhancement of magnetic coercivity as high as 2200 Oe. This study demonstrates that hard magnetic properties of the CoPt nanoparticles can be improved by controlling the cooling rate after heat treatments. [ABSTRACT FROM PUBLISHER]

Abstract: In-situ synthesis of magnetic nanocomposites with (NiFe2O4/CuO/FeO) crystal phases has been done using a sol–gel method by taking a non-stoichiometric composition of the precursors. The average particle size of the nanocomposites was calculated using X-ray diffraction (XRD) and high resolution tunneling electron microscope (HR-TEM) and it turns out to be ∼20nm. The vibrating sample magnetometer (VSM) measurements demonstrate the ferromagnetic nature of the nanocomposites. The synthesized nanocomposite was used to prepare magnetic fluid using tetramethylammonium hydroxide as a surfactant and its stability in the solution was also discussed. [ABSTRACT FROM AUTHOR]

Employing hydrothermal technique, undoped and nickel doped cerium oxide nanoparticles (Ni doped CeO 2 NPs) are synthesized with different concentration of dopant (5 M%, 10 M% and 15 M%). Prepared samples are subjected to Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), High resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), Ultraviolet–visible spectroscopy (UV–vis), Photoluminescence spectroscopy (PL), Vibrational sample magnetometry (VSM), Dielectric and electrical conductivity studies. Formation of CeO 2 NPs and Ni doped CeO 2 NPs is confirmed by PXRD and EDX. The crystallite size of the samples, determined from powder XRD using Williamson-Hall (W–H) plot, diminishes with increased Ni doping. The lattice parameter variation indicates an initial lattice contraction when the doping is less and a lattice expansion with enhanced Ni doping. These variations in crystallite size and lattice parameter could be due to the replacement of Ce ions by Ni ions in the CeO 2 lattice. SEM and HRTEM images show that the morphology of the NPs formed is nearly spherical. The UV–vis spectroscopic studies indicated that bandgap energy of Ni doped CeO 2 NPs widens as the Ni dopant concentration is increased. Increase of oxygen vacancy (V O) with increase in Ni concentration is designated by Raman spectra. The PL studies show that the nanoparticles of CeO 2 and Ni doped CeO 2 exhibit luminescence in the violet-blue-green wavelengths region (400 nm–500 nm). The decrease in emission intensity with increase of Ni concentration is indicative to increase of oxygen vacancies with increase in Ni content which act as non-radiative centers. VSM studies show that all the samples exhibit paramagnetism. The saturation magnetization and the retentivity of the samples increase as the Ni dopant concentration increases. All the samples display frequency dependent dielectric properties. With increase in the concentration of Ni dopant and frequency, a reduction in the values of dielectric constant and dielectric loss and an improvement in the electrical conductivity were observed for all the samples. [Display omitted] • (Å) could be due to the smaller ionic radius of Ni2+ (0.70 Å) than Ce4+ (0.97 Å). • Ce, Ni & O are present in desired amounts and no other impurities are detected. • TEM suggest that the Ni2+ dopant perhaps inhibit the growth of the cubic phase. • Between cerium cations & oxygen anions is expected to produce anti-ferromagnetic. • Grain boundaries hinder the mobility of electrons between ions. [ABSTRACT FROM AUTHOR]

A method for isolating single crystalline sub-5 nm carbon coated iron nanoparticles (Fe@C NPs) from a carbon nanotube matrix has been developed. The isolation of such particles allows for their characterization by high resolution electron microscopy methods and SQUID magnetometry. While the NPs are superparamagnetic at room temperature, at 10 K they exhibit a coercivity nearly 30 times greater than that of commercial Fe 3O 4NPs of comparable size. A novel nanotemplate directed assembly method for manipulating the particles at the individual particle level is also reported. [ABSTRACT FROM AUTHOR]

• The unique character of Indium when added in small amounts to Calcium-Barium M−type hexaferrite. • The sol–gel method was employed to prepare these compositions. • The structural properties gave an idea about the Indium incorporation in M−type hexagonal closed pack lattice. A series of Indium doped Calcium-Barium M−type hexaferrite with nominal compositions Ca 0.5 Ba 0.5 Fe 12-x O 19 In x (x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25) was prepared by sol–gel method. The x-ray diffraction (XRD) analysis of the synthesized compositions revealed two phases; M−type hexaferrite phase as a main phase and α-Fe 2 O 3 hematite phase. The gradual increasing trend in lattice parameters was observed on increasing Indium concentration showing incorporation of Indium in M−type hexagonal crystal structure. The grain size of M−type hexagonal phase was calculated using Debye–Scherer formula from non-overlapping peaks and it varied from 20 to 500 nm (0.5 μm). The scanning electron microscopy (SEM) micrographs showed hexagonal platelet-shaped, randomly distributed and agglomerated grains. The high resolution transmission electron microscopy (HRTEM) patterns further confirmed the observations of phases from x-ray diffraction (XRD). The remnant magnetization Mr and saturation magnetization Ms showed humped behaviour with maximum value for x = 0.25. The decrease in coercivity Hc was observed for x = 0.05 but it increased and remained nearly constant on further Indium addition. The effective dielectric constant showed resonance peaks at 4.3 and 8 GHz for all compositions and the effective loss decreases with frequency with maximum loss for x = 0.05, indicating the slight effect of In doping. The effective magnetic permeability showed small values and a resonance peak around 9 GHz, similarly magnetic losses also showed low values and a decreasing trend with frequency, not much noticeable influence of Indium doping was observed. These materials can be used in microwave frequency devices such as phase shifters and permanent magnets. [ABSTRACT FROM AUTHOR]

• The DO 3 structure alloy thin films of (FeCo)-(AlSi) have been successfully realized by DC magnetron sputtering. • The correlation between the soft-magnetic property and the DO 3 structure is experimentally verified. • Lower coercivity (4 Oe) and effective damping parameter (5 × 10−3) are achieved. The dependences of static and dynamic magnetic properties on both substrate deposition temperature (T S) and film-thickness (d) for (FeCo)-(AlSi) alloy thin films are discussed in conjunction with structure. The samples of a multi layered type (FeCo)-(AlSi) alloy thin films were fabricated at Ts by DC sputter-deposition onto (1 0 0) MgO substrates by using two targets of Fe 75 Co 25 and Al 50 Si 50. For the first time, the DO 3 phase in the quaternary alloy films are realized for T S at around 400 ℃ with d larger than 25 nm. The order parameter (S) was estimated by taking into account crystal structure factor, absorption factor, multiplicity factor, temperature factor, and Lorentz polarization factor. It is found that S increases with d , becoming nearly 1 for d larger than 50 nm. Observations by high resolution transmission electron microscopy support this result. The coercivity (Hc) and effective damping parameter (α eff) decrease with increasing d and remain nearly constant, approximately 4 Oe and 5 × 10−3, respectively. The result that H C decreases with increasing S suggests that (FeCo)-(AlSi) thin films with the DO 3 phase are an attractive candidate for future high frequency device applications. [ABSTRACT FROM AUTHOR]

• Mayan blue indigo. • Indigo molecule. • Second harmonic properties. • Magnetic properties. • HRTEM. • Raman spectroscopy. • X-ray photoelectron spectroscopy. • Mayan blue indigo exhibits magnetic and SHG properties useful for further applications in the treatment of cancer and in the development of electro-optical-magneto devices with smart pigments. In this work, we report new results on magnetic and second harmonic generation properties found in Mayan Blue Indigo (MBI) synthetic nanostructured pigment. MBI pigment was synthesized by a conventional method. Magnetization values were found to be 6.968 × 10−2 emu/g and 18.91 × 10−2 emu/g at 300 K and 50 K, respectively. Electron paramagnetic resonance spectra indicates unpaired electron signal appearing at the g-value of 2.49 with a peak-to-peak line width of 2114 G. Second harmonic generation properties were found at 483 nm. MBI pigment was analyzed using various characterizations techniques. The nano-structure and chemical surface characterization were confirmed by techniques that included high resolution transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The characterization results indicated, acicular nanostructures of ~1.14 nm, iron nanoparticles of ~1 nm, indigo molecule vibration mode at 632.52 cm−1, and binding energies corresponding to Fe (2s, 3s), O (1s, 2s), N (1s), C (1s), Si (2s, 2p), Al (2s, 2p), Mg (2s, 2p) related to the electronic structure of MBI nanostructured pigment. [ABSTRACT FROM AUTHOR]

• Coltan mineral from México. • Columbite and tantalite. • (Fe, Mn)Nb 2 O 6 and (Fe, Mn)Ta 2 O 6. • Coltan from México exhibits Magnetic and SHG properties useful for further applications in electro-optical-magneto devices. In this work, we report the novel findings on the structural, second harmonic and magnetic properties of the Coltan material from México. The magnetic properties were studied through the analyses of the magnetization versus temperature (M(T)) and magnetic field (M(H)). The isothermal magnetization measurements performed at 300 and 50 K shows a saturation magnetization of 11.5 and 11.8 emu/g, respectively. Electron Paramagnetic Resonance (EPR) signal result indicates a signal with g-value of g = 2.481 with a line width (ΔH PP) of 3575.7 G. Zero-field-cooling (ZFC) and Field cooling (FC) curves demonstrate the magnetic fingerprint of Coltan. Additionally, good second harmonic properties are observed at 470 nm, related to the blue color. High resolution transmission electron microscopy showed structural natural nanorods of Nb 2 O 5 at 50 nm resolution with interatomic distance of 0.39 nm. Finally, electronic chemical structure characterization by X-ray photoelectron spectroscopy results indicated binding energies of Fe (3p), Mn (3p), Nb (3d 5/2 , 3d 3/2 , 3p 3/2), O (1s), and Ta (4d 3/2) that correspond to columbite and tantalite related to chemical composition fingerprint of Coltan material from México. [ABSTRACT FROM AUTHOR]

The effects of the interface fluctuations on the magnetic properties of a Co/α-Al2O3/Co magnetic tunnel junction were intensively investigated using first-principles calculations. Hybridization of Co-3d and O-2p orbitals resulted in the covalent bonds between Co and three O atoms at the interface of Co(111)/α-Al2O3(0001) and, subsequently, interfacial Co atoms became undulated as much as 34.6% of the interlayer distance measured in the z direction. The magnetic moment of Co atoms at the rippled interface was enhanced to 1.95μB, while the value of the other ferromagnetic Co atoms remained unchanged. Significantly induced minority-spin density of states at the Fermi energy of the Co-interface atoms led to a highly negative spin polarization, -52.0%, at the junction interface. Interestingly, the spin polarization value for the barrier layer was in the range of -6.3%–59.2%. [ABSTRACT FROM AUTHOR]

High resolution electron microscopy (HREM) has been used to investigate the structure of Co(6 nm)/Cu(2.8 nm)/Co(4 nm)/MnFe(12 nm) spin valves so as to correlate the structure with the magnetic properties. The presence of a Ti seed layer enhances the structural quality of the film giving a strong <111> texture and large grain size. It is shown that the <111> texture favours a high exchange bias field. A numerical analysis of the HREM micrographs has been carried out in order to investigate more quantitatively the structure of the interfaces. It has been shown that locally they are diffuse over 2 monolayers in the growth direction. [ABSTRACT FROM PUBLISHER]

This article reports the fabrication and characterization of thin films of pure and cobalt doped ZnO (Co at 4% and 7%), a transparent diluted magnetic semiconductor (DMS) grown on 'Si' and glass substrates by RF magnetron sputtering technique. The crystalline structure and phase of the grown thin films were analyzed by using X-ray diffraction (XRD) method which confirmed the hexagonal wurtzite structure of the ZnO with slight lattice strain and change in orientation of the planes. The XRD also confirmed that, the films exhibit prominent peaks of (1 0 1) and (1 0 3) with polycrystalline nature. The morphology of the grown thin films was investigated by scanning electron microscopy (SEM) which confirmed the variation of micro-structure and size of the polycrystalline film's surface. The energy dispersive X-ray spectra (EDS) from SEM have confirmed the presence of constituent elements in the films and concentration (in %) of each element. The crystalline properties and morphology of the film's cross-section were studied by high resolution transmission electron microscopy (HR-TEM). The average thickness of the films was found to be about 600 nm from the cross-section electron microscopic images. The selected area electron diffraction (SAED) pattern from TEM was recorded for the Co (7%) doped ZnO film which has good polycrystalline quality. The optical transmittance of the films coated on corning glass substrates was investigated by UV–Visible spectrophotometer for pure, 4% and 7% Co doped ZnO films, which revealed the optical transparency of 85%, 75% and 65%, respectively. The room temperature ferromagnetism of the doped films was analysed by vibrating sample magnetometry and magneto optic Kerr effect. It was found that the ferromagnetic behaviour of films increases with 'Co' content and the results were discussed in detail. [ABSTRACT FROM AUTHOR]