Magnetic properties and photoabsorption of the Mn-doped CeO2 nanorods

Mn-doped CeO₂ nanorods have been prepared from CeO₂ particles through a facile composite-hydroxide-mediated (CHM) approach. The analysis from X-ray photoelectron spectroscopy indicates that the manganese doped in CeO₂ exists as Mn²⁺. The magnetic measurement of the Mn-doped CeO₂ nanorods exhibits an enhanced ferromagnetic property at room temperature with a remanence magnetization (Mr) of 1.36 × 10⁻³ emu/g and coercivity (Hc) of 22 Oe. Comparative UV-visible spectra reveal the shift of the absorption peak of the CeO₂ from ultraviolet region to visible light region after being doped with Mn. The room temperature ferromagnetic properties and light absorption of the Mn-doped CeO₂ nanorods would have potential applications in photocatalysis and building of photovoltaic devices.     

Structure and Magnetic Properties of Mn-doped CoFe 2 O 4 Nanoparticles Prepared by Solvothermal Route

Spinel Co_1?xMn_xFe₂ O ₄ (x = 0, 0.25, 0.5, 0.75 and 1.0) nanoparticles were synthesized by a solvothermal method using polyethylene glycol (PEG) as a surfactant. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray absorption near edge structure (XANES) spectroscopy and vibrating sample magnetometer (VSM) techniques were used to characterize phase, morphology, valence states, and magnetic properties of the samples. XRD analysis showed single phase of spinel structure, and the decrease of lattice constant on the effective Mn substitution was investigated. The effect of the PEG on the spherical aggregates of Co_1?xMn_xFe₂ O ₄ nanoparticles was observed. The result of XANES spectra showed Mn²⁺/Mn³⁺, Fe³⁺, and Co²⁺ exist in the samples. The samples showed ferromagnetism at room temperature with a maximum saturated magnetization of 72 emu/g and the smallest coercivity of 45 Oe for x = 1.0. The origin of ferromagnetic behavior is believed to be due to the occupation of Mn²⁺/Mn³⁺ ions.     

Optical properties of Mn-doped ZnS semiconductor nanoclusters synthesized by a hydrothermal process

Undoped and Mn-doped ZnS nanoclusters have been synthesized by a hydrothermal approach. Various samples of the ZnS:Mn with 0.5, 1, 3, 10 and 20 at.% Mn dopant have been prepared and characterized using X-ray diffraction, energy-dispersive analysis of X-ray, high resolution electron microscopy, UV-vis diffusion reflection, photoluminescence (PL) and photoluminescence excitation (PLE) measurements. All the prepared ZnS nanoclusters possess cubic sphalerite crystal structure with lattice constant a = 5.408 ± 0.011 ?. The PL spectra of Mn-doped ZnS nanoclusters at room temperature exhibit both the 495 nm blue defect-related emission and the 587 nm orange Mn²⁺ emission. Furthermore, the blue emission is dominant at low temperatures; meanwhile the orange emission is dominant at room temperature. The Mn²⁺ ion-related PL can be excited both at energies near the band-edge of ZnS host (the UV region) and at energies corresponding to the Mn²⁺ ion own excited states (the visible region). An energy schema for the Mn-doped ZnS nanoclusters is proposed to interpret the photoluminescence behaviour.     

Study of Semimagnetic Mn-Doped WO<Subscript>3</Subscript> Nanoparticles Synthesised by Precipitation Method: Hydrogenation Creates a Promising DMS

Abstract Tungsten oxide (WO₃) nanoparticles doped with different amounts of manganese ions (W_1?x Mn _x O₃, where x =?0.011, 0.022 and 0.044) were synthesised by hydraulic acid-assisted precipitation, followed by thermal calcinations. The powders were characterised by X-ray fluorescence (XRF), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS) and magnetic measurements. The monoclinic structure at room temperature (～293 K) found for un-doped WO₃ was preserved even with Mn doping. However, doping with Mn ions caused decease in unit-cell volume and slight increase in crystallite size (CS) of host WO₃. The hydrogenation was observed to corrode the crystallites without changing in crystalline structure. Controllable room-temperature ferromagnetic (RT-FM) properties were obviously observed with hydrogenated WO₃ doped with Mn. In addition, there existed an optimum doping concentration of Mn in WO₃ to obtain superior FM properties. Therefore, Mn-doped WO₃ nanopowders, owning to these amazingly tunable magnetic properties, could be considered a potential candidate for many applications partially required FM properties such as optical phosphors and catalysts.     

Tuning of optical,thermal and antimicrobial capabilities of CdS nanoparticles with incorporated Mn prepared by chemical method

Cadmium sulfide (CdS) nanoparticles with different amounts of incorporated Manganese (Mn: 10, 15 and 20 mol%) has been prepared by chemical method. In optical properties the UV–Vis–NIR absorption spectra of all samples showed blue shift compared with the bulk CdS and decrease in band gap with Mn concentration. The presence of functional groups was identified by fourier transform infrared spectroscopy. It confirmed presence of metal sulfur bonding and weak interaction between anions (S^2?) and cations (Mn²⁺). The Photoluminescence spectra showed two emission peaks at 397 and 541 nm corresponding to the electron-hole recombination of CdS and surface trap induced emission respectively. In thermal properties thermogravimetric curve indicated increase in weight loss with Mn incorporation suggesting that pure CdS nanoparticles are thermally more stable than Mn incorporated CdS nanoparticles. The antimicrobial activities of Mn incorporated CdS were studied against Gram-positive and Gram-negative bacteria as test microorganisms using agar plating-spot inoculation method.     

Structure and magnetic properties of (Co,Mn) co-doped ZnO diluted magnetic semiconductor nanoparticles

The ZnO, Zn_0.96Mn_0.04O, Zn_0.95Mn_0.04Co_0.01O, Zn_0.94Mn_0.04Co_0.02O and Zn_0.92Mn_0.04Co_0.04O nanoparticles were synthesized by simple chemical precipitation technique. The effects of co-doping on the structure and magnetic properties of these nanoparticles were studied. The X-rays diffraction (XRD) scans were performed in the 2θ range of 20°–80°. The XRD patterns, at 300 K, of all the pure and co-doped ZnO samples confirmed the formation of wurtzite-type structure. X-ray diffraction and transmission scanning electron microscope analysis indicated that the high spin Co²⁺ and Mn²⁺ ions were substituted for the Zn²⁺ ions at tetrahedral sites. The average size of the nanoparticles were increased from 17 to 24 nm with the increase of dopants concentration. Moreover, Energy Dispersive X-ray spectroscopy (EDX) confirmed the synthesis results. All Zn_0.96?xMn_0.04Co _x O (x?=?0.0, 0.1, 0.2 and 0.4) nanoparticles samples were observed to be paramagnetic below 300 K. However, a large increase in the magnetization was observed below 40 K. This behavior, along with the negative value of the Curie–Weiss constant obtained from the linear fit to the susceptibility data below room temperature, indicated the ferromagnetic nature of the samples. The origin of ferromagnetism is likely to be the intrinsic characteristics of the Co and Mn doped samples. The high magnetization was noted for the 1 wt% Co co-doped Mn–ZnO annealed samples as compared to other samples with Co concentration above and below this threshold concentration.     

Structural, optical and magnetic properties of Zn1 − xMnxO micro-rod arrays synthesized by spray pyrolysis method

Undoped and Mn-doped ZnO micro-rod arrays were fabricated by the spray pyrolysis method on glass substrates. X-ray diffraction and scanning electron microscopy showed that these micro-rod arrays had a polycrystalline wurtzite structure and high c-axis preferred orientation. Photoluminescence studies at 10 K show that the increase of manganese content leads to a relative decrease in deep level band intensity with respect to undoped ZnO. Magnetic measurements indicated that undoped ZnO was diamagnetic in nature whereas Mn-doped ZnO samples exhibited ferromagnetic behavior at room temperature, which is possibly related to the substitution of Mn ions (Mn^2 +) for Zn ions in the ZnO lattice.     

Effects of depositing rate on structure and magnetic properties of Mn:TiO2 films grown by plasma-assisted molecular beam epitaxy

We research the relationship between structural quality and magnetic ordering, using epitaxial Mn-doped anatase TiO₂ with excellent structural quality as a model system. Epitaxial films deposited slowly 0.08 (Å/s) possess a perfect crystalline structure, whereas films deposited at 0.2 (Å/s) are found to have a highly defected crystalline structure, as characterized by X-ray diffraction (XRD). X-ray photoelectron spectroscopy studies (XPS) indicate the possibility of hybridization between the Mn²⁺ ions and host defects. In contrast to defective Mn:TiO₂, these structurally superior films show negligible magnetism. It is demonstrated that room temperature ferromagnetism strongly correlated with the defect density of the sample.     

Effect of dopant concentration on the structural, electrical and optical properties of Mn-doped ZnO films

The Mn-doped ZnO (Zn_1 − xMn_xO) thin films with manganese compositions in the range of 0-8 at.% were deposited by radio-frequency (RF) magnetron sputtering on quartz glass substrates at room temperature (RT). The influence of Mn concentration on the structural, electrical and optical properties of Zn_1 − xMn_xO films has been investigated. X-ray diffraction (XRD) measurements reveal that all the films are single phase and have wurtzite structure with (002) c-axis orientation. The chemical states of Mn have been identified as the divalent state of Mn²⁺ ions in ZnO lattice. As the content of Mn increases, the c-lattice constant and the optical band gap of the films increase while the crystalline quality deteriorates gradually. Hall-effect measurements reveal that all the films are n-type and the conductivity of the films has a severe degradation with Mn content. It is also found that the intensity of RT photoluminescence spectra (PL) is suppressed and saturates with Mn doping.     

Influence of doping concentration on the properties of ZnO:Mn thin films by sol-gel method

Thin films of Mn-doped ZnO with different doping concentration (0.8, 1, 3, 5 at%) were prepared on Pt/Ti/SiO₂/Si substrates by using sol-gel method. The effects of the doping concentration on the structural properties, electrical characteristics and element binding energy in films were investigated. X-ray diffraction (XRD) results showed that the c-axis orientation of ZnO films was affected by Mn²⁺ content. Current-voltage (I-V) measurements indicated that resistivities of ZnO films were observably enhanced by dopant of Mn²⁺ and the resistivities value increased with a doping level up to 5 at% Mn. X-ray photoelectron spectroscopy (XPS) patterns suggested that the binding energies of O1s and ZnL₃M₄₅M₄₅ were affected by the content of Mn²⁺.     

Synthesis and Magnetic Properties of Mn-Doped and SnO2 Nanoparticles

This paper reports the synthesis of Sn_1?x Mn _x O₂ (for x=0, 0.01, 0.05 and 0.10) nanoparticles using the co-precipitation method. X-ray diffraction (XRD) results show that all samples are single phase with tetragonal crystalline structure. Rietveld refinements from XRD patterns show that the samples present particle average sizes of 4–30 nm confirmed by scanning electron microscopy. Magnetization results for SnO₂ nanoparticles at 5% and 10% of Mn synthesized at 800?°C exhibit a ferromagnetic behavior at room temperature and an increasing of the magnetization for increasing doping concentration. On the other hand, samples synthesized at 300?°C are paramagnetic.     

Structural and magnetic properties of Mn-doped ZnO nanorod arrays grown via a simple hydrothermal reaction

High density Mn-doped ZnO nanorod arrays were vertically grown on ITO substrate via hydrothermal reaction at relatively low temperature of 95 °C. The microstructure and magnetism of the arrays have been examined. Field emission scanning electron microscopy shows that the nanorods of 100 nm diameter and 1 μm length grow along the [001] direction. X-ray photoemission spectroscopy demonstrates that Mn is successfully doped into the nanorods. Meanwhile, all the Mn-doped ZnO nanorod arrays are ferromagnetic at room temperature. It is also found that the value of the saturation magnetization (M_s) of the ZnO nanorod arrays firstly increases with increasing the Mn concentration and then decreases. The higher M_s value is 0.11emu/g, which is obtained in the 5 at.% Mn-doped ZnO nanorod arrays. The ferromagnetism comes from the ferromagnetic interaction between the Mn ions, which partly replace Zn ions.     

Effect of Mn doping concentration on structural,vibrational and magnetic properties of NiO nanoparticles

The Ni_1?xMn_xO (x?=?0.00, 0.02, 0.04 and 0.06) nanoparticles were synthesized by chemical precipitation route followed by calcination at 500?°C for 4?h. The prepared samples were characterized by energy dispersive analysis of X-rays (EDAX), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). Rietveld refinement of XRD data confirms the structural phase purity and XRD patterns are well indexed to NaCl like rock salt fcc crystal structure with Fm-3m space group. The particle size of Mn doped samples is found to be less than that of pure NiO sample. However, the particle size increases slightly on increasing the Mn concentration due to surface/grain boundary diffusion. The vibrational properties of the synthesized nanoparticles were investigated by Raman and FT-IR spectroscopy. The results of room temperature magnetization (M-H) and temperature dependent magnetization (M-T) measurements are explained with a core-shell model. The synthesized nanoparticles show weak ferromagnetic and super-paramagnetic like behavior at room temperature.     

A Novel Approach for the Synthesis and Characterization Studies of Mn 2 + -Doped CdS Nanocrystals by a Facile Microwave-Assisted Combustion Method

A simple and efficient microwave-assisted combustion method was developed to synthesize Mn ²⁺-doped CdS (Mn _x Cd _1?xS: x= 0.0, 0.3, and 0.5) nanocrystallites. The study suggested that the application of microwave heating produced spherical shaped cluster of pure and Mn ²⁺-doped CdS nanocrystallites, which was achieved in few minutes. The effects of Mn ²⁺-doping on structural, morphological, optical and magnetic properties of CdS nanocrystallites were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high-resolution scanning electron microscopy (HR-SEM) with energy dispersive X-ray analysis (EDX), high-resolution transmission electron microscopy (HR-TEM) with selected area electron diffraction (SAED), UV-Visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and vibrating sample magnetometer (VSM). The XRD results confirmed the formation of hexagonal CdS. The formation of pure and Mn ²⁺-doped CdS phase was also confirmed by FT-IR and EDX. The formation of spherical shaped cluster of nanocrystallites was confirmed by HR-SEM and HR-TEM. The as-synthesized nanocrystallites were found to have good optoelectronic properties that were determined by DRS and PL spectra. VSM results of the as-synthesized Mn ²⁺-doped CdS nanocrystallites showed ferromagnetic behavior. Graphical Abstract

A simple and rapid microwave-assisted combustion method was developed to synthesize pure and Mn²⁺-doped CdS-nanocrystallites. The formation of spherical shaped cluster of nano-crystallites was confirmed by HR-SEM and HR-TEM. The optical properties were determined by DRS and PL spectra. Magnetic properties were analyzed by VSM.     

Magnetic and optical properties of Mn doped ZnO nanocrystalline films

We have investigated the properties of Mn-doped ZnO nanocrystalline film growing on zinc foil by the hydrothermal method. X-ray photoelectron spectroscopy shows that the manganese ions exist as Mn2+ in the film. From UV-vis spectra, we observe a red shift in wavelength of absorption and greater reflectivity due to the Mn ion incorporation in ZnO lattices. The photoluminescence spectrum of the Mn-doped ZnO film shows two strong new blue peaks centered at 424 nm and 443 nm, besides the UV emission peak owing to the band gap of ZnO semiconductor. The magnetic property of the Mn-doped ZnO exhibits a room temperature ferromagnetic characteristic with a saturation magnetization (Ms) of 0.3902 x 10(-3) emu/cm3 and a coercive field of 47 Oe. We suggest that the blue emission of the Mn-doped ZnO film corresponds to the electron transition from the level of interstitial Zn and Mn to the valence band. The defects brought about by Mn ion incorporation are the main cause of the room temperature ferromagnetic property.     

Local Atomic and Electronic Structure with Magnetism of La0.7Ca0.3Mn1?x Cu x O3 (x=0, 0.03, 0.06, 0.1)

Local atomic and electronic structure with magnetic properties, especially Griffiths phase, of polycrystalline samples La_0.7Ca_0.3Mn_1?x Cu _x O₃ (x=0, 0.03, 0.06, 0.1) have been studied. The X-ray absorption spectra (XAS) of Cu 2p core level prove that the valence state of Cu ions exhibits trivalent state when doping content x≤0.06 and divalent Cu²⁺ ions begin to show for x=0.1. For the valence states of Mn ions, the X-ray photoelectron spectroscopy data show that they are in mixed states of Mn³⁺ and?Mn⁴⁺, and a shift to lower binding energy is observed, which is not attributed to the variation of valence states of Mn ions but the change of crystallographic surroundings, because there is no obvious change detected by X-ray absorption fine structure spectroscopy (XAFS). The Debye-Waller factor (σ ²) of x=0.1 sample is only slightly larger compared to x=0, which may be the origin of enhancement of Griffiths phase observed in the inverse-susceptibility as a function of temperature (H/M～T). The H/M～T curves of Cu doped samples indicate coexistence of FM, AFM and PM phase above Curie temperature?T _C , which may be related to the strong hybridization of O 2p and Mn 3d reflected by O 1s XAS spectra.     

Synthesis, magnetization, and photocatalytic activity of LaFeO3 and LaFe0.9Mn0.1O3−δ

LaFe_0.9Mn_0.1O_3?δ and LaFeO₃ were synthesized and characterized by X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared, XPS techniques, UV–Visible absorption spectra techniques, vibrating sample magnetometer, and room temperature Fe⁵⁷ Mössbauer spectra. They were also evaluated for their photocatalytic activity toward the degradation of methyl orange under the sunlight irradiation. The experimental results show that the catalytic activities of the Mn-doped in LaFeO₃, i.e., LaFe_0.9Mn_0.1O_3?δ were much higher than those of LaFeO₃ due to its higher oxygen vacancies, variable valency Mn ions and the strong absorption in visible light, and it has higher magnetic property than that of LaFeO₃ due to the existence of Mn³⁺/Fe³⁺and Mn³⁺/Mn⁴⁺double exchange interaction in LaFe_0.9Mn_0.1O_3?δ. The LaFe_0.9Mn_0.1O_3?δ is the photocatalyst with intrinsic magnetic property and visible light activity, and it is applicable to the magnetic separation process for its higher saturated magnetization (M _s), lower coercivity (H _c), and remanent magnetization (M _r) as well as the superparamagnetic contribution in the sample, and it can be reusable and maintain relatively high activity.     

Structural, optical and photoluminescence studies of heavily Mn-doped ZnO nanoparticles annealed under Ar atmosphere

Undoped and heavily Mn-doped with ZnO nanoparticles (Zn_1?xMn_xO, x?=?0.0, 0.05, 0.1 and 0.2) annealed under Ar atmosphere have been synthesized by a sol–gel method. The structural properties and optical absorption of the prepared samples have been examined by powder X-ray diffraction, energy dispersive X-ray analysis, Fourier transform infrared (FTIR) spectroscopy and UV–visible spectrophotometer. Hexagonal wurtzite structure of the samples is confirmed by the XRD spectra. The average crystalline size of the Zn_1?xMn_xO nanoparticles has been calculated from X-ray line broadening and is decreased from 35.73 to 18.24?nm with increase in Mn concentrations from 0.0 to 0.2. The increase in lattice parameters indicates the substitution of Mn in ZnO lattice. SEM and TEM photographs indicated that the grain size of undoped ZnO is bigger than the Mn-doped ZnO which is due to the limitations of grain growth upon Mn doping. The presence of functional groups and the chemical bonding due to Mn doping is confirmed by FTIR spectra. PL spectra of the Zn_1?xMn_xO system showed that the shift in near band edge emission at 390?nm and a blue band emission at 450–490?nm which confirms the substitution of Mn.     

A new synthesis of hexadecylamine-capped Mn-doped wurtzite CdSe nanoparticles

Hexadecylamine-capped Mn-doped wurtzite CdSe nanoparticles have been successfully synthesized via a novel, facile method at low temperature. Optical spectroscopy, X-ray diffraction (XRD), electron paramagnetic resonance (EPR) transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area diffraction (SAD) and energy dispersive spectroscopy (EDS) measurements are presented to confirm successful doping of the wurtzite CdSe. The nanoparticles obtained show quantum confinement in their optical properties with band-edge luminescence. The reduction in the emission intensity of the doped CdSe compared to the pure CdSe indicates the presence of impurity (Mn²⁺ ions) in the pure CdSe nanoparticles. XRD analysis reveals that the nanoparticles are of wurtzite structure while the HRTEM image confirms the crystallinity of the doped material.     

Synthesis and growth mechanism of triangular Mn doped CdS nanowires

Triangular Mn-doped CdS nanowires (NWs) were prepared by thermal evaporation of a mixture of CdS and MnCl₂. The morphologies and detailed structures were characterized by a scanning electron microscope, X-ray diffraction, and transmission electron microscope. The Mn concentration plays an important role in synthesis of the triangular NWs. The morphologies can be varied from hexagonal to triangular by adjusting the amount of MnCl₂ in the reaction mixture. The oriented attachment mechanism is demonstrated to be the most suitable mechanism to explain the growth process of the triangular NWs. The photoluminescence shows the intensity of Mn²⁺ emission peak increases as the molar ratio of MnCl₂increases.