Sm Doping Research Articles

Influence of Metal (Al, Mg, Sm, and Cu) Dopants on Structural, Optical, Magnetic, and Antimicrobial Properties of ZnO Nanopowders Synthesized by Coprecipitation Method

Pure and metal‐doped ZnO nanopowders with composition formula M0.04Zn0.96O (where M = Al, Mg, Sm, and Cu) are synthesized using the coprecipitation method. The structural characterization of synthesized powders is investigated using X‐ray diffraction and the results confirm the hexagonal wurtzite structure without any additional phases. The change in structural parameters of ZnO with dopants is estimated using X‐ray peak profile analysis. The structural characterization is further analyzed by Fourier‐transform infrared spectroscopy. The size and morphology of the synthesized powders are analyzed by a field‐emission scanning electron microscope, which also evidences the formation of uniform nanostructures with quasi‐spherical and hexagonal shapes. Moreover, the elemental composition of these metal‐doped nanotructures is determined by energy‐dispersive X‐ray measurements. UV–vis spectroscopy is used to determine the energy bandgap of ZnO nanopowders. A vibration sample magnetometer is employed to measure the samples' magnetic properties, and dopants are found to induce distinct magnetic behaviors in ZnO. The antimicrobial activity of the synthesized powders is measured using the well diffusion method. It is observed that the introduction of dopant metals leads to increased microbial activity. Among the doped ZnO variants, Al‐doped ZnO exhibits the highest level of microbial activity compared to pure ZnO and other samples.

Catalytic action and bactericidal behavior of samarium/carbon spheres-doped manganese oxide nanostructures and their molecular docking analysis

The co-precipitation technique was adapted to synthesize different concentrations (2 % and 4 %) of samarium (Sm) doped constant equates of carbon spheres (Cs) and manganese oxide (MnO2). The principal objective of this investigation is to demonstrate confirmation that Sm/Cs-doped MnO2 nanostructures (NSs) owned antibacterial and catalytic attributes. Reduction in surface area manifested to agglomeration, NSs faces become inaccessible to initiate a reaction, can be overcome upon doping of Sm. Sm has the potential to increase the activity of metal oxide ascribed to its electron trapping effect. The structural morphologies, optical properties, functional groups, elemental composition, and d-spacing were determined by applying various characterizations. With the incorporation of CS and Sm, UV–vis spectra shifted towards lower wavelength and band gap energy (Eg) was reduced. MnO2 possessed orthorhombic structure, according to the XRD pattern and TEM exhibited long Burr-like morphology of undoped MnO2. SAED image illustrated that MnO2 is polycrystalline. 4 % Sm/CS doped MnO2 revealed the highest degradation (91 %) in a neutral environment. Furthermore, 4 % Sm/Cs doped-MnO2 revealed an inhibitory zone of 2.85 mm against Escherichia coli (E. coli). Additionally, an analysis of molecular docking revealed a binding interface with NRs and the functional domains of certain cellular proteins. Results indicated that Cs-doped MnO2 and Cs/Sm-doped MnO2 NRs are the most potent DNA gyrase and FabB enzyme inhibitors.

Structural, Magnetic, and Mössbauer Investigation of Mg-Ni-Co ferrites doped by Sm3+ sions

Samarium-doped magnesium-nickel-cobalt nanoferrites (Mg1/3 Ni1/3Co1/3)Fe2−xSmxO4, with x = 0.00, 0.01, 0.02, 0.04, and 0.08, were synthesized by the coprecipitation method. X-ray diffractometer (XRD), transmission electron microscopy (TEM), energy dispersive x-ray (EDX), x-ray photoelectric spectroscopy (XPS), Fourier Transform Infra-Red (FTIR), Raman spectroscopy, Mössbauer spectroscopy, and magnetic measurement techniques were used, to study the structure, microstructure, and magnetic properties of the samples. The formation of the cubic spinel structure was confirmed by Rietveld analysis of the XRD data and by the appearance of the two absorption bands close to 400 cm−1 and 600 cm−1 from the FTIR spectrum. Raman spectroscopy verified the formation of the spinel phase in the samples. The elemental composition, valency, and cationic distribution were examined using x-ray photoelectric spectroscopy (XPS) measurements. Experimental findings revealed that doping with Sm3+ ions had a significant effect on the magnetic properties of nanoparticles. The saturation magnetization (M s ) and coercivity field (H c ) values fluctuate depending on the crystallite size (DXRD) of the samples from XRD analysis as the Sm3+ content increases. The magnetization dependence on the applied field was investigated at different ranges of applied fields based on the output of the statistical parameters for the curve fitted using four different forms of the law of approach to saturation. The statistical parameters and physically significant fitted parameters give information on the dependence of magnetization over various applied field regions. A thorough investigation of the output parameters from fitting into various equations reveals that the composition of Mg-Ni-Co ferrites exhibits a dependence of magnetization on the applied field. Room-temperature Mössbauer spectra displayed a mix of the magnetic sextet and central quadrupole doublet, with improvement in the magnetic sextet in the Sm-doped samples. Moreover, Mössbauer spectra at 77 K showed the demise of the quadrupole doublet in all samples and showed two sextets (tetrahedral and octahedral sites). Sm-doping reduced the values of the hyperfine magnetic field of both sextets. All Fe ions can be found in the Fe3+ state, according to the isomer shift values and there is a migration of Fe3+ ions from octahedral to tetrahedral sites upon Sm doping, which was confirmed by XPS measurements.

Influence of samarium modification on the phase-change performance and phase structure of tin antimonide

This work presents the optimization of the crystallization behavior and reliability of Sn15Sb85 thin films by doping Sm element. The phase transition behaviors induced by thermal were investigated by in situ resistance measurement. With the addition of Sm element, Sn15Sb85 film exhibits the superior crystallization temperature (232 °C) and data conservation (172.32 °C for 10 years), larger activation energy of crystallization (4.91 eV) and crystalline resistance (∼103 Ω), which contributes to the increased thermal stability of the amorphous state and decrease in the programming energy. The Sm-doping can broaden the energy band gap from 0.55 to 1.07 eV. The amorphous Sm and Sn compositions could retard grain growth and refine grain size from 21.13 to 11.13 nm, combining with x-ray diffraction and x-ray photoelectron spectroscopy. The surface morphology of Sn15Sb85 film becomes smoother after Sm doping as determined by atomic force microscopy images, resulting in the improved interfacial reliability. Phase change memory devices based on Sm0.095(Sn15Sb85)0.905 films can successfully achieve the complete SET and RESET reversible operation process with high operating speed (200 ns) and low power consumption (1.6 × 10−10 J). The results suggest that doping the proper concentration of Sm element will be an effectual solution to adapt and optimize the crystallization properties of Sn15Sb85 phase change material.

Influence of Sm doping on the optical, mechanical, electrical, thermal and z-scan analysis of sulphamic acid single crystal for nonlinear optical device applications

Influence of Sm doping on the optical, mechanical, electrical, thermal and z-scan analysis of sulphamic acid single crystal for nonlinear optical device applications

Samarium addition-mediated simultaneous achievement of excellent resistance drift and superior thermal stability in phase-change compound antimony-selenium thin film

The Sm-doped Sb7Se3 thin films were systematically investigated, including phase change behavior, phase structure, microstructure, and electrical properties. The in-situ resistance test displays that the addition of Sm element leads to a significant increase in the crystallization temperature, decadal data retention and crystallization activation energy, implying better thermal stability. Crystallization kinetic analysis indicates a one-dimensional growth crystallization pattern, exhibiting an ultra-fast crystallization speed. The change in optical bandgap reflects that the exotic Sm atoms enhance the bandgap energy, which facilitates the reduction of the threshold current. Resistance drift test highlights the suppression of structural relaxation by Sm atoms, which would greatly improve the reliability of the information readout. X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectra, and transmission electron microscopy demonstrate that the addition of Sm retards the crystallization process and refines the grain size. Energy dispersive spectroscopy shows that the Sm dopant has incorporated into Sb7Se3 thin film. The phase change memory cell based on Sm-doped Sb7Se3 film exhibits faster running speed (100 ns) and lower power consumption (3.0 × 10−11 J) than the conventional Ge2Sb2Te5 material. All the results prove that incorporating appropriate amounts of Sm into Sb7Se3 material is an ideal technique for optimizing resistance drift and thermal stability of Sb7Se3 thin films.

Efficient Photocatalytic degradation of direct blue 15 dye using samarium doped bismuth tungstate nanosheets: A sustainable approach towards wastewater treatment

The rare earth metal, samarium (Sm3+) doped bismuth tungstate (Bi2WO6) nanoparticles were prepared by a one-pot hydrothermal method. The powder X-ray diffraction (XRD) analysis confirmed the formation of Bi2WO6 with an orthorhombic crystal structure. The crystallite size of Bi2WO6 decreased from 20.73 to 9.25 nm as the Sm substitution in the W lattice increased. The vibrational modes of W–O, Bi–O, and Sm–O were identified in the range of 500–900 cm−1. The optical bandgap of Sm3+ doped Bi2WO6 nanoparticles increased from 2.86 to 2.95 eV with higher Sm doping levels. The surface morphology revealed the formation of flower-like sheets in the Sm3+ doped bismuth tungstate. The energy dispersive X-ray (EDX) spectrum of Sm3+ doped Bi2WO6 nanoparticles confirmed the presence of Sm, Bi, W, and O without any other impurities. The small peak detected at 1082.14 eV in the survey scan of Sm3+ doped Bi2WO6 nanoparticles belonged to Sm3d. In the photocatalytic degradation of direct blue 15 (DB15) under visible light irradiation, the efficiency of the nanoparticles increased with higher Sm3+ concentration. The obtained results demonstrated that the Sm–Bi2WO6 nanosheets could provide an effective and sustainable solution for treating the wastewater containing direct blue 15 dye.

Deep insights into the promotion role of Sm doping in the sulfur resistance of Fe2O3 catalyst for NH3-SCR: A combined experimental and DFT study

To investigate the inherent role of Sm doping in metal sulfation over the surface of Fe2O3 catalyst and reveal the reason for the SO2 tolerance enhancement of Sm/Fe2O3 catalyst at low temperatures (<320 °C), sulfated Fe2O3 and Sm/Fe2O3 catalysts were prepared by pretreating fresh catalysts in SO2+O2 atmosphere. Selective catalytic reduction (SCR) of NOx by NH3 activities and physicochemical characteristics of fresh and sulfated catalysts were studied, and the reaction mechanisms on sulfated catalysts analyzed. The minor shift of Fe signal to high value and larger shift of S signal to low value of sulfated Sm/Fe2O3 compared with sulfated Fe2O3 was observed with X-ray photoelectron spectroscopy (XPS), indicating that Sm modification could weaken the sulfation of active Fe sites. Consistent with the XPS results, density functional theory calculations showed that SO2 is more easily adsorbed on the Sm/Fe2O3 catalyst with the adsorption sites located at Sm atom and its neighboring Fe atoms. In-situ DRIFTS results showed that the SCR reaction over the sulfated Fe2O3 catalyst followed both L-H (the adsorbed NH3 species react with adsorbed nitrate species) and E-R (the adsorbed NH3 species react with gaseous NO) mechanisms at 250 °C, with the L-H route much faster, whereas only the L-H pathway occurred over sulfated Sm/Fe2O3 catalyst because of too strong affinity of NH3 on the sulfated sites to inhibit NH3 activation – this was also the reason for its enhanced Lewis and Brønsted acidity. More reactive nitrate species were formed on the sulfated Sm/Fe2O3 catalyst due to the existence of more un-sulfated Fe sites, making the Sm/Fe2O3 catalyst resistant to SO2 poisoning at relatively low temperatures.

Effects of Sm doping on EuB6

A solid-state reaction was used to investigate the nanocrystalline particles of Sm-doped EuB6 and their optical, thermionic emission and mechanical properties were investigated. The tapered nanoawls had a length of 3–12 μm and a diameter ranging from 40 to 200 nm at the roots and 20–100 nm at the tip as shown by in scanning electron microscopy (SEM). As the temperature of the material increases, the thermionic emission current density also increases. Jo as the zero-field current densities for Eu0.6Sm0.4B6 at 1500 K, 1673 K, 1773 K, 1873 K were 0.72 A cm-2, 4.25 A cm-2, 10.06 A cm-2 and 20.05 A cm-2. By increasing the Sm doping content, electrical density of Eu1-xSmxB6 decreases. In all materials, the electrical resistivities increased linearly with temperature from 200 to 1200 °C, indicating metallic conductivity. Eu0.6Sm0.4B6 has a lower Vickers hardness and higher flexural strength than EuB6.

Optical characterization of Sm3+ doped phosphate glasses for potential orange laser applications

Undoped and Sm3+doped 45P2O5–45Na2O–2Al2O3–8BaO glasses were synthesized by the melt-quenching technique. The glass structure and luminescence properties were investigated by using Raman spectroscopy, scanning electron microscopy (SEM), spectroscopic ellipsometry, Judd-Ofelt theory and photoluminescence. Electron microscopy showed the homogeneity of samples. Raman spectroscopy revealed that the overall structure of the glass was unaffected by the doping of Sm3+ and ellipsometry was used to measure the optical constants. Judd-Ofelt (JO) analysis was performed on the absorption bands of Sm3+ (4f5) and the three phenomenological parameters (Ω2, Ω4, and Ω6) were computed and then used to determine radiative properties such as the radiative transition probability (Ar), the fluorescent branching ratio (βr), the stimulated emission cross-section (σe) and the radiative lifetime (τrad). Photoluminescence (PL) spectrum showed the typical four transitions of Sm3+ at wavelengths of 564, 600, 645 and 703 nm corresponding to 4G5/2 → 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively. The spectroscopic quality factors Ω4/Ω6, the predicted lifetime (τrad) calculated using the JO method and the experimentally lifetime (τexp) for the 4G5/2 level were calculated and discussed. The glass color purity is as high as 98%, which makes it a potential candidate for laser emission.

Application of samarium doped lanthanum nickel oxide perovskite nanocatalyst for biodiesel production

The catalytic performance of the synthesized LaNiO3 (LNO) and LaSmNiO3 (L1-xSxNO) perovskite structures as novel efficient catalysts for the conversion of waste cooking oil (WCO) to biodiesel was evaluated. The synthesized heterogeneous catalysts of LNO and L1-xSxNO were characterized via Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), Transmission Electron Microscopy (TEM), Brunauer, Emmett, and Teller (BET), inductively coupled plasma-optical emission spectrometer (ICP-OES), and Power X-ray diffraction (XRD). The crystal size of LNO was obtained to be around 31 nm at 2θ of 47.31° using Scherrer's equation. Catalysts characterization revealed that doping Sm with LNO (L0.9S0.1NO) enhanced the surface area from 7.71 to 15.75 m2/g, and thus may provide more active sites for transesterification reaction. Also, the Sm doping causes numerous oxygen vacancies in the structure of perovskite, improving the catalyst's ability to catalyze reactions. To determine the optimum conditions in the WCO transesterification process, the response surface methodology (RSM) based central composite design (CCD) was applied. The influences of key parameters including MeOH/WCO ratio (5–20 mol/mol), reaction duration (1–5 h), catalyst mass fraction (1–5 wt%), and reaction temperature (60–120 °C) were explored on the behavior of the reaction. It is inferred that the L0.9S0.1NO catalyst has excellent catalytic activity in converting WCO to biodiesel. The experimental and modeling sensitivity analysis indicated that the application of L0.9S0.1NO catalyst led to the WCO conversion of 95.14 % to biodiesel at MeOH/WCO ratio of 9.07, reaction duration of 3.02 h, catalyst mass fraction of 3.08 wt%, and reaction temperature of 80.07 °C.

Sputtered nanocrystalline samarium doped CuO photoelectrode for efficient photoelectrochemical water splitting

Copper oxide (CuO) is a promising photoelectrode for photoelectrochemical (PEC) energy generation because of its fascinating properties, including high earth availability and inexpensive. In this context, samarium (Sm)-doped CuO thin films are deposited on a glass substrate through the sputtering technique to serve as photocatalysts in PEC water splitting. The structural characterizations of sputtered films were performed with X-ray diffraction (XRD) spectroscopy, while the morphology and elemental composition of all films were studied with the help of field-emission scanning electron microscopy (FE-SEM) connected with a dispersive energy X-ray analyzer. XRD pattern has shown that all films are polycrystalline with a preferred orientation of (−111) crystallographic plane. FE-SEM images and ImageJ analysis showed that all deposited particles are uniformly distributed as disassembled particles over the substrate area. The optical energy band gap (Eg) was increased by adding the Sm contents in the CuO films. The photocurrent density for the photoelectrode was improved by Sm dopants as compared to the pure sample and recorded its maximum value of − 4.66 mA/cm2 at ∼ − 0.385 V vs. RHE which was about 4 times higher than that of the pure sample with feasible photostability retention. Additionally, the value of the charge transfer resistor for the CuO photocathode with the smallest amount of Sm ions was the lowest as compared to other photocathodes. These results offer a practical method for creating a brand-new fabrication technique for PEC devices with remarkable water-splitting efficiency.

Theoretical investigations of electronic structure, magnetic and optical properties of CdS-X (X= Sm, La, Ce) materials for optoelectronic applications

Current research is based on density functional theory investigations of structural, electronic, magnetic, and optical properties of X (X = Sm, La, Ce) doped CdS using Wien2k code. Spin-polarized calculations indicate non-magnetic character of pure and La doped CdS while magnetism is noticed upon Sm and Ce doping into CdS. Hubbard correction indicate shift of f-states toward the Fermi level and non-negative frequency modes in phonon spectra illustrate dynamical stability of proposed materials for synthesis. However, magnetic moment in Ce doped CdS (2.9188 μB) is larger than Sm doped CdS (2.7901 μB). Cd 4d-states, S 3p-states, La 5d-, Sm and Ce 4f-states show supreme role around the Fermi level which improve electronic properties. Reduction in band gap is noted which points good conduction. Optical absorption spectrum of impurities added CdS materials exhibit blueshift. Moreover, enhanced absorption and upgraded conductivity along with increasing refractive index of selected materials emphasize their potential uses in high energy UV photonics, sensors, spintronics, optoelectronics and energy harvesting devices.

The promotion of NH3-SCR performance and its mechanism on Sm modified birnessite

To develop novel NH3-SCR catalysts with low-temperature and high-efficency, a series of birnessite (δ-MnO2) catalysts with different Sm doping by methanol reduction are synthesized. The results showed that the introduction of Sm successfully inhibited the crystallization of MnOX, promoted the specific surface area, the contents of chemisorbed oxygen species and the formation of surface acid sites. It also increased the relative content of (Mn4+ + Mn3+)/Mn, which was beneficial to low-temperature SCR activity. The catalytic performance of xSm/Mn (δ-MnO2 based with xSm doping) catalysts was evaluated by NH3-SCR performances. Among them, 0.05 Sm/Mn showed 100% NOX conversion and high N2 selectivity compared to the other Sm addition catalysts within the operating low-temperature window (25–200 °C), at a high GHSV (gas hourly space velocity) of 60,000 h−1. The modified 0.05 Sm/Mn catalysts followed the L-H and E-R reaction mechanisms and were dominated by L-H, as revealed by in-situ DRIFTs analysis.

Sm doped Co3O4: Development of a low-cost high-performance photodetector for optoelectronic devices

Undoped and Sm doped cobalt oxide (Co3O4) thin films were successfully deposited onto bare glass substrates using a nebulizer spray technique. The Sm weight concentration varied from 1 % to 4 %. To investigate the effects of doping on the crystal shape, structure, emission, and light absorption characteristics of the deposited Co3O4 films, an analysis employing various analytical techniques was carried out. The electrical properties of the thin films are studied utilizing a Keithley source meter. All of the developed Co3O4 films reveal a cubic spinel structure. Nanocrystalline grains and some overgrown clusters are seen in the Co3O4 morphology and were found to vary with the concentration of Sm (1, 2, 3, and 4 wt%). With a rise in the number of Sm dopants in the Co3O4 films, the mean grain size is observed to increase as observed through FESEM images. The energy-dispersive X-ray examination of the Co3O4:Sm 3 % sample confirms the presence of Co, O, and Sm elements. The 3 % Sm-doped Co3O4 thin film exhibits a greater absorption value and a lower transmittance, according to the optical studies. Additionally, it was revealed that the optical band gap value decreases from 2.23 to 2.11 eV and 1.48–1.45 eV as Sm doping concentration was increased from 0 % to 3 %. The 3 % Sm doped Co3O4 thin film sample reveals a maximum photocurrent of 9.32 × 10−5A. Thus it is established that the addition of Sm doping to Co3O4 increases its photo detecting capabilities, making it a favorable option for use in photo-detectors.

Sm doped ZnO-SnO2 nanocomposites with improved photo-degradation strength and antibacterial properties

In this work, we devoted our effort to synthesize rare-earth (Sm3+) doped ZnO-SnO2 nanocomposites by sol-gel method to address issues like wastewater treatment and minimization of bacterial infection. Successful formation of multi-phase nanocomposites of hexagonal ZnO and tetragonal SnO2 has been confirmed by x-ray diffraction (XRD) analysis. The effect of Sm doping is understood from the enhancement in ZnO grain growth and shift in diffraction peaks. The morphology study by FESEM reveals the variation in sample morphology with Sm doping with energy-dispersive analysis of x-ray (EDAX) study providing the confirmation on the existence of Sm ions in the crystal lattice of ZnO-SnO2 heterostructure. Transmission electron microscopic (TEM) study manifests the formation of two distinct types of particles (hexagonal & spherical) corresponding to ZnO and SnO2 which has been further clarified from the measurement of lattice spacing from the high-resolution TEM images and indexing of selected area electron diffraction (SAED) pattern. The near band edge emission (NBE) of ZnO is blue shifted along with the evolution of oxygen vacancy defects which induced new bands at 488 nm and 613 nm upon Sm doping. Further, intra-4f transitions of Sm3+ ions have also been observed at 560 nm, 590 nm and 638 nm linked to 4G5/2– 6HJ (J = 5/2, 7/2, 9/2) transitions. The Zn, Sn, O, and Sm elements are confirmed to exist in the nanocomposite according to the X-ray photoelectron spectroscopy (XPS) investigation which provided information on the chemical composition and electronic states of the material. Photocatalytic degradation study of toxic environmental dyes like methylene blue (MB), Congo red (CR) and methyl orange (MO) shows that Sm3+ ions in ZnO/SnO2 helps to enhance the degradation efficiency by the formation of Z-scheme heterojunctions between ZnO and SnO2. This allows the delay in recombination rate of the photoinduced electron/hole pairs. The antibacterial behavior of the prepared nanocomposites against E. Coli and S. Aureus has also been studied in detail which demonstrates improved antibacterial efficiency of the samples.

Mechanistic investigation of Sm doping effects on SO2 resistance of W-Zr-ZSM-5 catalyst for NH3-SCR

The WO3-ZrO2 for NH3-SCR catalyst has excellent NO conversion, especially at high temperature, which are appropriate for the diesel engine after-treatment system. However, the diesel engine NH3-SCR catalysts can be affected by SO2 toxicity. Thus, a series of xSm-WZZ catalysts were prepared by sol–gel method, and the Sm species as the promoter were applied to enhancing the SO2 resistance and regeneration performance of the catalyst. 1Sm-WZZ catalyst exhibited the best SO2 and H2O resistance and slightly improved the NH3-SCR activity, in which 100% NO conversion and N2 selectivity can be achieved at 400–600 ℃. Moreover, compared with WZZ catalyst, 1Sm-WZZ catalyst showed excellent regeneration performance, which could be regenerated by thermal treatment at 350 ℃. The results of XPS, CO2-TPD and H2-TPR revealed that the Sm could decrease the amount of alkaline sites and redox ability of catalyst, which may be the main reason for the reduction of the adsorption and oxidation of SO2. Additionally, the Sm decreased the formation of ammonium sulfate salts on catalyst, which were verified by the TGA and FTIR spectrum experiments. Furthermore, the Sm could preferentially react with SO2 than chemisorbed oxygen, which restrains the reaction of chemisorbed oxygen with SO2, thereby reducing the generation of sulfate around the chemisorbed oxygen. In addition, the in-situ DRIFTS tests indicated that the Sm could reduce the generation of S = O for tridentate sulfate species and SO3 on the catalyst.

Schottky Barrier Control of Self-Polarization for a Colossal Ferroelectric Resistive Switching.

Controlling the domain evolution is critical both for optimizing ferroelectric properties and for designing functional electronic devices. Here we report an approach of using the Schottky barrier formed at the metal/ferroelectric interface to tailor the self-polarization states of a model ferroelectric thin film heterostructure system SrRuO3/(Bi,Sm)FeO3. Upon complementary investigations of the piezoresponse force microscopy, electric transport measurements, X-ray photoelectron/absorption spectra, and theoretical studies, we demonstrate that Sm doping changes the concentration and spatial distribution of oxygen vacancies with the tunable host Fermi level which modulates the SrRuO3/(Bi,Sm)FeO3 Schottky barrier and the depolarization field, leading to the evolution of the system from a single domain of downward polarization to polydomain states. Accompanied by such modulation on self-polarization, we further tailor the symmetry of the resistive switching behaviors and achieve a colossal on/off ratio of ∼1.1 × 106 in the corresponding SrRuO3/BiFeO3/Pt ferroelectric diodes (FDs). In addition, the present FD also exhibits a fast operation speed of ∼30 ns with a potential for sub-nanosecond and an ultralow writing current density of ∼132 A/cm2. Our studies provide a way for engineering self-polarization and reveal its strong link to the device performance, facilitating FDs as a competitive memristor candidate used for neuromorphic computing.

Study of low-temperature magnetic properties of the antiferromagnetic topological insulator Sm-doped MnBi2Te4

MnBi2Te4 is the first discovered intrinsic magnetic topological insulator. It has great research significance and is related to new phenomena such as topological magneto-electric effect and quantum anomalous Hall effect (QAHE). We report first doping of rare-earth elements in MnBi2Te4 crystals. MnBi2Te4 crystalline samples with different Sm doping ratios were synthesized, and Sm atoms may enter the lattice and replace Mn atoms. Low-temperature magnetization measurements show that, in addition to the antiferromagnetic (AFM) transition of MnBi2Te4, some doped samples undergo small-scale ferromagnetic transitions at around 15 K. Doping furthermore reduces the magnetic field required for the transition to the canted AFM (CAFM) state and slightly increases the Néel temperature of the crystal. Our results suggest that doping rare-earth elements may be a feasible method for tuning the magnetism of MnBi2Te4 and for future applications of magnetic topological insulators.

Improved magnetic, optical, electrochemical, and structural properties of copper ferrite through the optimized addition of samarium dopant using the co-precipitation method

For the feasible application of photocatalysis technology at an industrial scale, demand for visible-light-driven photocatalysts with excellent superparamagnetic properties for easy separation has soared. In this work, the magnetic, optical, electrochemical, and structural properties of copper ferrite nanoparticles were improved by optimizing the amount of Sm dopant (SmxCuFe2-xO4, where x = 0, 0.03, 0.06, 0.09, 0.12, 0.15) added during synthesis. Sm-CF-0.06 was found to be the optimized synthesized material as it shows high crystallinity (30.9 nm) and saturation magnetisation (52.6 emu/g) which was accompanied by small coercivity (58.5 Oe) and remanent magnetisation (6.13 emu/g). In addition, Sm-CF-0.06 exhibited faster movement of electrons on the surface of the material and demonstrated effective charge separation of photo-generated electrons and holes as observed from cyclic voltammograms and Nyquist plots respectively. The synthesized materials exhibited superparamagnetic properties and their bandgap was found to be in the range of (1.56–1.62 eV) which gave them an edge for separation using external magnets and allow the utilizing abundant visible light, respectively. Lastly, the structural properties, surface morphology, internal structure, purity, and porosity of the synthesized materials were fully evaluated.