Magnetic Semiconductors Research Articles

Mn doping nanoarchitectonics of NiO nanoparticles with various property impacts for optoelectronic devices and diluted magnetic semiconductor applications

Mn doping nanoarchitectonics of NiO nanoparticles with various property impacts for optoelectronic devices and diluted magnetic semiconductor applications

Lanthanide‐Based Molecular Magnetic Semiconductors

AbstractMagnetic semiconductors, with integrated properties of ferromagnets and semiconductors, are significant for developing next‐generation spintronic devices. Herein two atomically precise clusters of dysprosium(III) tellurides, formulated respectively as [Na2(15‐crown‐5)3(py)2][(η5‐Cp*Dy)5(Te)6](py)4 (Dy5Te6, Cp*=pentamethylcyclopentadienyl; py=pyridine) and [K(2,2,2‐cryptand)]2[(η5‐Cp*Dy)6(Te3)(Te2)2(Te)3] (Dy6Te10), are reported. Crystallographic studies revealed the presence of multifarious tellurido ligands within the polyhedral cluster cores. Spectroscopic and magnetic studies showed that both clusters are single‐molecule magnets exhibiting slow magnetic relaxation behaviors at low temperatures and semiconductors with low optical band gaps comparable to benchmark semiconductors. These clusters represent probably the first lanthanide‐based molecular magnetic semiconductors.

The electronic and magnetic properties of Cr-doped ZnO monolayer at higher percentage by first principles calculations

The crystal structure, structural stability, electronic band structures and magnetization of Cr-doped ZnO monolayer (ML) have been investigated by GGA+U method using first principles calculations in this work. The stability of these systems is confirmed by the negative formation energies at different Cr concentrations. The calculated band gaps with and without the Hubbard U correction aligned well with other computational results. With the increase of Cr concentration, the band gap of Cr-doped ZnO monolayer decreases for the spin-up configuration. However, in the spin-down configuration, the band gap increases first and then decreases and the maximum band gap is obtained at 22.22% Cr concentrations. At 33.33% Cr concentration, the ZnO ML exhibits metallic behavior. The density of states (DOS) analysis reveals an asymmetric nature, indicating ferromagnetism in Cr-doped ZnO MLs at various concentrations, with a magnetic moment per Cr atom of approximately 3.99 μB. The total magnetic moment rises with increasing Cr concentration. Charge density difference analysis shows increased magnetization with higher Cr concentration. At 22.22% Cr concentration, the ZnO ML exhibits ferromagnetism and semiconducting properties, suggesting significant potential for spintronic applications as a diluted magnetic semiconductor.

Doping dependent magnetic and thermoelectric response of perovskite BaGeO3 for spintronics and energy applications

Using ab-initio simulations, we have investigated the magnetic and thermoelectric response of the pristine and Mn-, Ni-, and In-doped BaGeO3 at Ge-site. The dopants Mn, Ni, and In can be doped at Ge-site due to lower formation energies. The dopants significantly alter the electronics properties of BaGeO3. Interestingly, the In-BaGeO3 exhibits half-metallic nature. Furthermore, our doped system exhibit the magnetic behaviour with 100 % polarization near Fermi level. Additionally, the spin orientation favors the ferromagnetic (FM) states for Mn-BaGeO3. Furthermore, the realization of magnetic anisotropy energy (MAE) may pave the way to use BaGeO3 for applications in magnetic devices. Moreover the zT (0.95) is enhanced for In-BaGeO3. Thus, our studied configuration could potential candidate for thermoelectric insulation as well as thermoelectric cooling applications. We are expecting that our findings could open the ways to utilize the BaGeO3 in the domain of spintronics and magnetic semiconductor devices applications.

Insulator-to-Metal Transition and Isotropic Gigantic Magnetoresistance in Layered Magnetic Semiconductors.

Magnetotransport, the response of electrical conduction to external magnetic field, acts as an important tool to reveal fundamental concepts behind exotic phenomena and plays a key role in enabling spintronic applications. Magnetotransport is generally sensitive to magnetic field orientations. In contrast, efficient and isotropic modulation of electronic transport, which is useful in technology applications such as omnidirectional sensing, is rarely seen, especially for pristine crystals. Here a strategy is proposed to realize extremely strong modulation of electron conduction by magnetic field which is independent of field direction. GdPS, a layered antiferromagnetic semiconductor with resistivity anisotropies, supports a field-driven insulator-to-metal transition with a paradoxically isotropic gigantic negative magnetoresistance insensitive to magnetic field orientations. This isotropic magnetoresistance originates from the combined effects of a near-zero spin-orbit coupling of Gd3+-based half-filling f-electron system and the strong on-site f-d exchange coupling in Gd atoms. These results not only providea novel material system with extraordinary magnetotransport that offers a missing block for antiferromagnet-based ultrafast and efficient spintronic devices, but also demonstrate the key ingredients for designing magnetic materials with desired transport properties for advanced functionalities.

Giant Valley Zeeman Splitting in Vanadium-Doped WSe2 Monolayers.

2D dilute magnetic semiconductors (DMS) based on transition metal dichalcogenides (TMD) offer an innovative pathway for advancing spintronic technologies, including the potential to exploit phenomena such as the valley Zeeman effect. However, the impact of magnetic ordering on the valley degeneracy breaking and on the enhancement of the optical transitions g-factors of these materials remains an open question. Here, a giant effective g-factors ranging between ≈-27 and -69 for the bound exciton at 4K in vanadium-doped WSe2 monolayers, obtained through magneto-photoluminescence (PL) experiments is reported. This giant g-factor disappears at room temperature, suggesting that this response is associated with a magnetic ordering of the vanadium impurity states at low temperatures. Ab initio calculations for the vanadium-doped WSe2 monolayer confirm the existence of magnetic ordering of the vanadium states, which leads to degeneracy breaking of the valence bands at K and K'. A phenomenological analysis is employed to correlate this splitting with the measured enhanced effective g-factor. The findings shed light on the potential of defect engineering of 2D materials for spintronicapplications.

Imaging Strain-Controlled Magnetic Reversal in Thin CrSBr.

Two-dimensional materials are extraordinarily sensitive to external stimuli, making them ideal for studying fundamental properties and for engineering devices with new functionalities. One such stimulus, strain, affects the magnetic properties of the layered magnetic semiconductor CrSBr to such a degree that it can induce a reversible antiferromagnetic-to-ferromagnetic phase transition. Using scanning SQUID-on-lever microscopy, we directly image the effects of spatially inhomogeneous strain on the magnetization of layered CrSBr, as it is polarized by a field applied along its easy axis. The evolution of this magnetization and the formation of domains is reproduced by a micromagnetic model, which incorporates the spatially varying strain and the corresponding changes in the local interlayer exchange stiffness. The observed sensitivity to small strain gradients along with similar images of a nominally unstrained CrSBr sample suggest that unintentional strain inhomogeneity influences the magnetic behavior of exfoliated samples.

Calculation of Curie Temperature and Carriers Effective Masses of (Ga, Mn)As Diluted Magnetic Semiconductor from the Eight-Band k.p Model

An important step toward the development of spintronic information processing, transfer, and storage devices is the discovery of a dilute magnetic semiconductor (DMS) that demonstrates carrier-mediated ferromagnetism and maintains its magnetic properties above room temperature. Despite considerable progress made in recent decades, the maximum Curie temperature (∼200 K) remains well below room temperature. Mndoped GaAs are among the various diluted magnetic semiconductor materials that have been studied and have emerged as one of the most promising contenders for technological usage. The key characteristic of GaMnAs is its ferromagnetic properties, which are critical for spintronic devices. The primary goal of this work is to compute two critical properties of GaMnAs: the effective masses and the Curie temperature. The 8-band k.p model put forth by Kane was utilized to compile the GaMnAs band parameters using a MATLAB program. Our calculations are based on Lowdin perturbation theory, where spin-orbit, sp-d exchange interaction, and biaxial strain are taken into account. We calculated the Curie temperature of the GaMnAs alloy, within the mean-field approach based on the Zener model. Our findings demonstrated a direct proportionality relationship between the Curie temperature and the hole concentration (p) in GaMnAs. Moreover, we looked into how the Mn content and strain affected the effective masses of electrons, heavy, and light holes that were calculated for various crystallographic directions in GaMnAs. The effective masses that were calculated were highly dependent on the Mn content, which ranged from 1% to 5%, and the strain, which varied from −2% (tensile strain) to 2% (compressive strain).

Examining the influence of electric field on the photoionization cross section and spin polaronic shift in a semimagnetic double quantum well

In the current research, we performed a numerical investigation of a shallow donor impurity confined in a diluted magnetic semiconductor (DMS) double quantum well (DQW) made of a Cd1−xwMnxwTe/Cd1−xbMnxbTe under the applied electric field in the z-direction. The optoelectronic properties were carried out using the effective-mass approximation and the variational method. The binding energy and photoionization cross section were examined by considering different factors such as, well width, barrier width, impurity position, and Manganese mole fraction. Additionally, the spin polaronic shift corrections to the donor binding energy, caused by the strong exchange interaction between the magnetic moment of the Mn2+ the confined carrier spin, have been examined under the aforementioned effects.

Diamagnetic to Ferromagnetic Like Transition of Non-Stoichiometry Barium Titanate (BaTiO3-x) Prepared by Sol-gel Method

The oxygen vacancy properties are significant, creating ferromagnetic properties of material in metal oxide systems like dilute magnetic semiconductors. An aqueous sol-gel method has been used in the present study to synthesize non-stoichiometry BaTiO3-x polycrystalline. In an attempt of examining the oxygen deficiency consequences on the magnetic properties, the gel samples were sintered (1000◦C) at various times (6, 12, 18, and 24 hours) under a vacuum environment. This study employs an X-ray diffraction apparatus in terms of characterizing segments and structures of the samples. It also investigates morphology and element distribution on the surface of the samples exploiting an Electron microscope where Energy dispersive spectroscopy is supplied. For the purpose of characterizing the magnetic properties of the samples, it applies vibrating sample magnetometers. The chemical state of the element and its corresponding bond to other elements was identified using X-ray photoelectron spectroscopy. Single-phase compounds were observed. The crystal system is tetragonal, but the crystal parameters are different. Increase sintering time leads to increase crystallite size and decrease in micro strain. Moreover, sintering in a vacuum environment results in oxygen deficiency and leads to the atomic ratio of Ba/Ti change as the sintering time increases. The Ba/Ti ratio change affects the transformation from diamagnetic to ferromagnetic-like. The elements (Ba, Ti and O) chemical state is shown and its bonding to the corresponding element along with the X-ray photoelectron spectroscopy pattern of the BTX2 sample. The element of oxygen binds to Ti and Ba while Ba element exists in two chemical states.

Magnetic and electronic properties of 1D hybrid nanoobjects composed of alternating polycyclic hydrocarbon regions and double carbon chains

It has been proposed recently that 1D hybrid nanoobjects consisting of alternating double carbon chains and polycyclic carbon regions can be obtained from graphene nanoribbons of alternating width by electron irradiation. Here, based on density functional theory calculations, we show that magnetic and electronic properties of such nanoobjects can be changed dramatically by modifying the chain length and edge structure of polycyclic regions and this opens wide possibilities for spintronic applications. Nanoobjects composed of polycyclic regions with dangling bonds and even chains are found to behave as magnetic semiconductors that can generate spin-polarized currents. Band gaps of nanoobjects with odd chains change considerably upon switching between magnetic states making them promising for magnetic tunnel junctions. We also demonstrate that use of a hybrid exchange–correlation functional is important to properly describe stability of magnetic states, band gaps and synergistic effects of nanoobject components leading, for example, to magnetism in even chains.

Structural, optical, and dielectric properties of Mn-doped Ce1-xMnxO2 nanocrystals for frequency-dependent device applications

Cerium oxide (CeO2) is a significant oxide semiconductor known for its advantageous electrical, optical, and dielectric properties. This study investigates the effects of manganese (Mn) doping on the structural, optical, and dielectric characteristics of CeO2. Pure and Mn-doped Ce1-xMnxO2 nanocrystalline powders, with Mn concentrations of 0, 1, 3, 5, and 7 %, were synthesized using a co-precipitation method. Structural analysis confirmed the formation of a cubic crystal structure, while surface morphology revealed agglomerated spherical particles. Notably, the band gap of Ce1-xMnxO2 decreased from 2.80 eV to 2.30 eV with increasing Mn content, indicating enhanced electronic properties due to doping. The dielectric properties exhibited a pronounced frequency dependence, with significant variations in dielectric constant and loss, demonstrating the potential of Mn-doped CeO2 as a diluted magnetic semiconductor. These findings underscore the material's applicability in biosensors and optoelectronic devices, paving the way for advancements in frequency-related technologies.

Investigation of Spintronic Properties of Transition Metal Doped ZnO Thin Films Produced by Sol-Gel Spin Coating

Transition metal-doped diluted semiconductor materials have attracted significant interest in spintronic applications. In order to investigate the structural, optical, electrochemical, and magnetic properties of these diluted magnetic semiconductors, transition metal-doped ZnO thin films were successfully produced at room temperature using a low-cost sol-gel spin coating technique with the same molar ratios. XRD analyses revealed that all samples adopted the crystal structure of ZnO. Optical measurements indicated high transparency in the visible region for all samples, while electrical measurements confirmed that all samples were n-type semiconductors. Finally, magnetic measurements showed that pure ZnO and Al-doped ZnO exhibited diamagnetic behavior, while Ni and Co doped ZnO displayed magnetic behavior. These results show that Co and Ni-doped ZnO films can be used as diluted magnetic semiconductor materials in spintronic applications.

Computational survey of optoelectronic properties and half-metallicity in ZnFeMnS: insight from first principles calculations

The electronic structure, optic and magnetic properties of the ZnFeMnS quaternary compound are studied on the basis of band-structure calculations, using full-potential linearized augmented plane wave (FPLAPW) method. The calculations are performed within the generalized gradient approximation (GGA). The calculated results indicate that ternary ZnMnS has an insulating character for the two directions of spin so, in its current form, it is inappropriate for spintronics devices. In contrary, Fe/Mn codoped ZnS is a half-metallic (HM) ferromagnet with a magnetic moment of 9 μB per formula unit. The integer magnetic moment of this compound indicates the stability of its half-metallic behavior. Consequently ZnFeMnS could be a promising dilute magnetic semiconductor for application in spintronic devices. Moreover, we have computed optical properties (absorption coefficient and reflectivity) of the two compounds, and have found a pronounced peak occurring at low energies for ZnFeMnS in all the optical curves due to transition metal (TM) impurity. The improvement of optical properties allows this compound to be used in manufacturing photovoltaic static converter or in display devices.

Two-Dimensional Magnetic Semiconductors by Substitutional Doping of Monolayer PtS2

Two-Dimensional Magnetic Semiconductors by Substitutional Doping of Monolayer PtS₂

First-principles study on the electronic structure, magnetic and optical properties of strain regulated (V, Mn) co-doped HfS2 monolayer

The impact of biaxial strain on the electronic structure, magnetic and optical properties of double impurity co-doped HfS2 monolayers was investigated using first principles methods. The findings indicate that (V, Mn) co-doped HfS2 monolayer behaves as a dilute magnetic semiconductor both before and after the application of strain, with its magnetism attributed to the hybridization of V:3d, Mn:3d, and S:3p orbitals. In the biaxial strain range of −5% to 5%, the ferromagnetism remains unchanged, the band gap decreases with the increase of compressive strain. In contrast, tensile strain leads to an increase in both the band gap. Finally, our analysis of optical properties reveals that (V, Mn) co-doped HfS2 monolayer enhances infrared light absorption coefficient, compressive strains further enhance this absorption coefficient. These results indicate that (V, Mn) co-doped HfS2 monolayer by strain regulation is an effective strategy for designing dilute magnetic semiconductors and optoelectronic devices.

Electronic and magnetic properties of Janus ZrSSe monolayer doped with V impurity and VX3(X = C, N, O, and F) clusters

In this work, doping with V impurity and VX3 (X = C, N, O, and F) clusters is proposed to modify the electronic and magnetic properties of Janus ZrSSe monolayer. Pristine ZrSSe monolayer is an indirect-gap semiconductor two-dimensional (2D) material with energy gap of 0.73 eV. This value is reduced to 0.13 eV under effects of single Zr vacancy, which corresponds to the reduction of the order of 82.19%. V impurity magnetizes significantly ZrSSe monolayer, inducing feature-rich magnetic semiconductor nature. Herein, the magnetism with a total magnetic moment of 1.00 μ B is produced mainly by V-3d orbital. Investigations indicate that the antiferromagnetic state with zero total magnetic moment is stable when V impurities are located close to each other. Further separating impurities causes the antiferromagnetic-to-ferromagnetic state transition, such that a total magnetic moment of 2.00 μ B is obtained. ZrSSe monolayer is metallized by doping with VC3, VN3 and VF3 clusters. In the first two cases, the non-magnetic nature is preserved. Meanwhile, significant magnetization with a total magnetic moment of 3.00 μ B is achieved by VF3 cluster substitution. Similarly, VO3 cluster induces significant magnetic properties in ZrSSe monolayer with a total magnetic moment of 1.00 μ B , which are originated mainly from the antiparallel spin orientation between V atom and Se atoms closest to the doping sites. Herein, VO3 cluster substitution in ZrSSe monolayer makes new magnetic semiconductor 2D material. The Bader charge analysis indicates that all four clusters attract charge from the host monolayer. Our work may introduce efficient approaches to modify the ZrSSe monolayer electronic and magnetic properties towards spintronic and optoelectronics applications.

Optimization of structure, optical, magnetic, and radiation shielding properties of ZnO@xSrFe12O19 nanocomposites

In this work, the pristine ZnO, SrFe12O19 (SFO), and their nanocomposites (ZnO/x SFO: x = 1, 3 and 5%) were synthesized by co-precipitation and sonomechanical method. The x-ray diffraction data validate the preparation of ZnO, SFO, and nanocomposite samples with high phase purity. The optical band gap was calculated from UV–vis-NIR diffuse reflectance measurements, and it was modified by increasing SFO content. Adding 1, 3, and 5 wt% of SFO to the ZnO matrix showed ferromagnetic characteristics for the nanocomposites with a squareness ratio of around 0.49, which considered these nanocomposites as a magnetic semiconductor suitable for digital memory and spintronic applications. Additionally, the radiation shielding features of the prepared samples were evaluated. The shielding parameters for the studied samples were obtained using the Phy-X/PSD program. The fast neutron removal cross-section of SFO was 0.094 cm−1, the highest among the investigated samples, while the composites had similar values, about 0.083 cm−1. The results indicated that the γ--ray attenuation ability and the values of exposure buildup factor for the prepared samples were close. Therefore, ZnO, SFO, and their nanocomposites compared to stationary shielding materials (SMs), can be candidates for applications where radiation protection is needed.

Cr-doped CdS and ZnS nano/microstructures with ferromagnetic properties

Transition-metal-doped cadmium sulfide (CdS) and zinc sulfide (ZnS) dilute magnetic semiconductors have attracted widespread research interests due to their potential spin electron applications. Most theoretical and experimental analyses have focused on studying their optical properties. In response to the widespread application of dilute magnetic semiconductor nanomaterials in electronic components, semiconductor chips, integrated circuits and other fields, dilute magnetic semiconductors with room-temperature ferromagnetic chromium (Cr)-doped cadmium sulfide and zinc sulfide nanostructures were synthesized using the solvothermal method. According to X-ray diffraction analysis, the products of chromium-doped cadmium sulfide and zinc sulfide were clearly determined to be a hexagonal phase. Scanning electron microscopy images showed that the morphologies of cadmium sulfide and zinc sulfide with different contents of chromium were mainly composed of nanorods and a micro-floral shape. Energy-dispersive X-ray spectroscopy measurements indicated that the synthesized products were composed of chromium, cadmium (Cd), zinc (Zn) and sulfur (S). Vibrating-sample magnetometry showed that undoped cadmium sulfide exhibited weak ferromagnetism at room temperature, and undoped zinc sulfide exhibited diamagnetism, while chromium-doped cadmium sulfide and zinc sulfide had strong ferromagnetism. The saturation magnetization M s of chromium-doped cadmium sulfide (chromium = 4.21%) was about 9.524 × 10−3 emu/g; the coercivity H c was about 98.327 Oe. The saturation magnetization M s of chromium-doped zinc sulfide (chromium = 7.67%) was about 8.502 × 10−3 emu/g; the coercivity H c was about 96.237 Oe. The ferromagnetism of chromium-doped cadmium sulfide and zinc sulfide was attributed to the double-exchange mechanism.

Effect of spin quantum force on lower and upper hybrid waves’ instability under the influence of an electron beam in a magnetized semiconductor plasma

Effect of spin quantum force on lower and upper hybrid waves’ instability under the influence of an electron beam in a magnetized semiconductor plasma