Magnetic Semiconductors Research Articles

Doping Dy improves magnetism and electricity in hexagonal boron nitride

Dy-doped hexagonal boron nitride with a circular flaky structure and a diameter of 50 nm was prepared through high-temperature reduction reactions. The hexagonal boron nitride nanosheets (hBNNSs) exhibit both room-temperature ferromagnetism and semiconductor conductivity properties. Doping with Dy transforms hBNNSs from insulators to magnetic semiconductors. The saturation magnetization of hBNNSs with a Dy doping content of 0.58 at.% at room temperature is 0.1405 emu/g. This suggests that the Curie temperature of Dy-doped hBNNSs is above room temperature. With increasing temperature, the current of the hBN film rises, demonstrating semiconductor conductive behavior. First-principles calculations indicate that the magnetic properties of the material primarily arise from the f-orbital electrons of the Dy element, while the electrical properties are mainly attributed to the Fermi energy level crossing of the conduction band, influenced by the f-orbital and d-orbital electrons of the Dy element.

Electronic and magnetic properties of layered M3Si2Te6 (M = alkaline earth and transition metals)

Recently, a new layered material, Mn3Si2Te6, was identified to be a semiconductor with nodal-line topological property and ferrimagnetic ground state. In this work, we propose a series of structures, M3Si2Te6 (M = alkaline earth and transition metals), and systematically investigate their mechanical, magnetic and electronic properties, and the strain effect to enrich the family of the layered materials for practical applications. We find 13 stable M3Si2Te6, including 5 semiconductors (M = Ca, Sr, Fe, Ru and Os) and 8 metals (M = Sc, Ti, Nb, Ta, Cr, Mo, W and Tc). Two structures (M = Ti and Cr) are antiferromagnetic (AFM), while other structures are non-magnetic (NM). Similar to Mn3Si2Te6, the AFM structures exhibit magnetic anisotropy energies (MAEs) and semiconductors have anisotropic electron effective masses. We further show that compressions along the z-axis can effectively tune the electronic and magnetic properties, such as the semiconductor-metal and NM-AFM transition in Fe3Si2Te6, the two-fold degeneracy of the valence band maximums in Sr3Si2Te6, as well as the reduced MAE for all magnetic structures. These results demonstrate the diverse properties of the layered M3Si2Te6 family and provide promising theoretical predictions for the future design of new layered materials.

Intrinsic room-temperature ferromagnetism in a two-dimensional semiconducting metal-organic framework

The development of two-dimensional (2D) magnetic semiconductors with room-temperature ferromagnetism is a significant challenge in materials science and is important for the development of next-generation spintronic devices. Herein, we demonstrate that a 2D semiconducting antiferromagnetic Cu-MOF can be endowed with intrinsic room-temperature ferromagnetic coupling using a ligand cleavage strategy to regulate the inner magnetic interaction within the Cu dimers. Using the element-selective X-ray magnetic circular dichroism (XMCD) technique, we provide unambiguous evidence for intrinsic ferromagnetism. Exhaustive structural characterizations confirm that the change of magnetic coupling is caused by the increased distance between Cu atoms within a Cu dimer. Theoretical calculations reveal that the ferromagnetic coupling is enhanced with the increased Cu-Cu distance, which depresses the hybridization between 3d orbitals of nearest Cu atoms. Our work provides an effective avenue to design and fabricate MOF-based semiconducting room-temperature ferromagnetic materials and promotes their practical applications in next-generation spintronic devices.

First-principles investigates on the electronic structure and magnetic properties of V-, Cr-, Mn-doped two-dimensional Ga2O3

In this paper, the electronic and magnetic properties of transition metals (TM) doped two-dimensional (2D) Ga2O3 are investigated based on first-principles calculations. The formation energies under O-rich conditions are significantly lower than those under O-poor conditions, making it easier to synthesize the TM-doped 2D Ga2O3 systems under O-rich conditions. The introduction of V, Cr, and Mn has successfully introduced magnetism into 2D Ga2O3. The V3+, Cr3+, and Mn3+ ions are left with 2, 3, and 4 unpaired electrons occupying different d orbitals, further leading to magnetic moments of 2, 3, and 4 μB in the three doped systems, respectively. Biaxial strain can effectively manage the bandgap of the TM-doped Ga2O3 systems. This work proves that doping V, Cr, and Mn into 2D Ga2O3 is an effective way to broaden the application of 2D Ga2O3 in dilute magnetic semiconductor (DMS)-based devices.

Lanthanide atoms doped arsenene monolayer: Enhanced magnetic anisotropies, huge magnetic moments and significant strain-modulated effects

Employing the spin-polarized density functional theory (DFT), we investigated the magnetic and optical properties of buckled arsenene (β-As) after doping a whole series of lanthanide (Ln) atoms. Our results demonstrate that Ln atoms can be stably doped into the single layer arsenene. Upon doping Ln atoms, La, Ce, Pr, Nd, Gd, Dy and Lu@arsenene behave dilute magnetic semiconductor (DMS) properties, while the Pm, Sm, Eu, Ho, Er and Tm@arsenene show half metallic characteristics. Most of Ln@arsenene systems favor the long-range ferromagnetic ordering. The maximum of Ln-doped systems' magnetic moments and magnetic anisotropy energy (MAE) can reach 8 μB and 7.48 meV, respectively. The doping of Ln atoms into arsenene improves the optical responses in visible and infrared regions. Strain can alter the magnetic coupling between Sm and the neighboring As atoms and reduce the system's magnetic moment. Besides, strain can improve the MAE of these systems, accompanied by the change of the easy magnetization of Sm@arsenene. Furthermore, compressive and tensile strains effectively improve the optical responses in visible and ultraviolet region, respectively. Based on the obtained results, we believe that the Ln@arsenene monolayer has application prospects in photoelectronics and spintronics such as high-density memory devices.

Electronic, Magnetic, and Optical Tunability of SiP Monolayers via 3d Transition‐Metal Doping

Herein, the electronic, magnetic, and optical properties of direct‐band semiconducting SiP monolayers (MLs) doped with 3d transition‐metal (TM) atoms are investigated using first‐principles calculations. The results indicate that TM (TM = Sc, Ti, Co, Ni, Cu, and Zn)‐doped SiP MLs are nonmagnetic, while TM (TM = V, Cr, Mn, Fe)‐doped ones exhibit prominent magnetic moments. Specifically, V‐, Cr‐, and Fe‐doped SiP MLs are magnetic semiconductors and Mn‐doped SiP ML is a spin gapless semiconductor, where the contributions of the TM atoms to magnetic moments are dominant and the contributions of the nearest Si and P atoms are either small or negligible. Furthermore, the TM (TM = V, Cr, Mn, Fe) doping can enhance the carrier mobility in certain directions and result in highly in‐plane anisotropic mobility behaviors. In addition, the TM (TM = V, Cr, Mn, Fe) doping can not only broaden the optical absorption range of SiP ML to the infrared region, but also enhance the optical absorption coefficients of SiP ML in the visible region. These results provide insights into the TM doping effect on the electronic, spintronic, and optical properties of SiP MLs and may be useful for related applications based on SiP MLs.

Surface functionalization of graphene-like boron arsenide monolayer: a first-principles study

In this work, the effects of hydrogen (H) and oxygen (O) adsorption on the electronic and magnetic properties of graphene-like boron arsenide (BAs) monolayer are investigated using first-principles calculations. Pristine monolayer is a non-magnetic two-dimensional (2D) material, exhibiting direct gap semiconductor character with band gap of 0.75 (1.18) eV as calculated by generalized gradient approximation with Perdew–Burke–Ernzerhof (HSE06) functional. Four high-symmetry adsorption sites are considered, including on-top of B atom (), on-top of As atom (), on-top of hollow site (), and on-top of bridge site (). Using the criterion of adsorption energy, it is found that and sites are favorable adsorption sites for H and O adatom, respectively. The analysis of electronic interactions indicate the charge transfer from host BAs monolayer to both adatoms. H adsorption conducts to the emergence of magnetic semiconductor nature in BAs monolayer with a total magnetic moment of 1.00 . Herein, the magnetism is originated mainly from H adatom and its neighbor As atoms. In contrast, the non-magnetic nature of BAs monolayer is preserved upon absorbing O atoms. In this case, the energy gap exhibits a slight reduction of 4%. Further, the effects of adatom coverage are also analyzed. The presented results suggest an effective modification of ground state electronic properties, as well as induction of new feature-rich properties to make new multifunctional 2D materials from non-magnetic BAs monolayer.

Effect of NM (B, C, N, O and F) doping and Fe[sbnd]NM co-doping on structure, electronic and magnetic properties of monolayer 2H[sbnd]MoTe[formula omitted] : A first principle investigation

Exploring magnetism in two-dimensional transition-metal dichalcogenides (TMDs) has gained a plethora of interest in recent times. Herein, employing spin-polarized density functional theory, we looked into the effect of non-metal doping (B, C, N, O, and F) and Fe-non metal co-doping on structure, electronic, and magnetic properties of 2HMoTe2 to identify new promising configurations for spin-based device applications. For non-metal doping, the results depict that B, N, and F-doped systems are magnetic, and the N-doped system shows magnetic-semiconducting behavior. The half-metallic Fe-doped MoTe2 transforms into a magnetic semiconductor upon co-doping. The structural distortion around the Fe atoms modifies the crystal field splitting, resulting in triply degenerate a1 and singly degenerate a2 and a3 states. Uncompensated electrons in the co-doped system and hybridization between Fe and NM atom modifies the magnetic properties of monolayer MoTe2. Competition between crystal field splitting and intra-atomic Hund’s exchange splitting determines the magnetic moment. Due to charge compensation, C-doped and FeC co-doped systems are non-magnetic. N-doped and FeN co-doped MoTe2 exhibit long-range magnetic ordering. Formation energy calculations revealed that the co-doped configurations are easily attainable in experiments compared to non-metal doped systems. The results open up a robust way to realize 2HMoTe2 based spintronic devices.

Enhancement of magnetic stability and absorption properties of monolayer NiZr magnetic semiconductor by electric field modulation

The effect of the external electric field on the electronic structure, magnetic properties, dielectric function and absorption properties of monolayers NiZr are investigated in this manuscript. It is found that monolayer NiZr exhibits antiferromagnetic, ferrimagnetic, and ferromagnetic properties under the external electric field. The magnetic property is affected by both the crystal field and the external electric field, and the magnetic moment is nonlinearly related to the intensity of the external electric field. Under the electric field −0.01 V/Å and 0.055 V/Å, the ferromagnetism of monolayer NiZr is stable, while is unstable under other electric field. The magnetic property mainly comes from the spin of Zr atom, and the electron transfer between Ni atom and Zr atom is not equal, indicating the existence of free electrons and p-d hybrid orbitals. The Ni d orbital and Zr d orbital are split into dxy, dyz, dxz, dxx-yy, and dzz five orbitals. The Zr dzx and Ni dzy orbital spin are primary contributed to the magnetic properties of monolayers NiZr under electric field of −0.01 V/Å; whereas Zr dxx-yy and Ni dxx-yy orbitals spin contribute primarily under 0.055 V/Å. The dielectric constant and absorption characteristics are increased, the anisotropy is weakened, and the effect of electric field on the absorption characteristics is weakened under the [110] direction electric polarization. Therefore, [110] direction electric polarization is beneficial in improving the absorption characteristics of monolayers NiZr.

Evolution of Relaxor‐Type High‐k Dielectric in Bulk Pristine Cu2+ and Li+ Co‐Substituted Wurtzite ZnO

AbstractDielectric constants determine the level of miniaturization in capacitive components involved in electronic devices. Cu‐Li co‐doping is attempted to introduce the multiferroic relaxor nature of dielectricity and dilute magnetism in the bulk material simultaneously as Li+ ion substitution in ZnO lattice is known to form acceptor states within the band gap of ZnO and paramagnetic Cu2+ present in ZnO lattice can introduce dilute magnetism. Phase purity and substitution of Cu2+ and Li+ ions in ZnO lattice along with oxide‐ion vacancy formation was confirmed using Powder x‐ray diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive X‐ray analysis (EDX), X‐ray Photoelectron Spectroscopy (XPS), Inductively Coupled Plasma Mass Spectrometry (ICP‐MS) and Magnetic property measurement system (MPMS) studies. The dielectric constant (ϵr′) of bulk pristine Zn0.92Cu0.05Li0.03O and Zn0.9Cu0.05Li0.05O is found to be 18000 and 20000 respectively at 1000 Hz frequency at 600 °C. Both dielectric constant and dielectric loss were decreasing with increasing frequencies. The increase in dielectric constant (ϵr′) with increasing temperatures at different frequencies for Zn0.92Cu0.05Li0.03O1‐δ and Zn0.9Cu0.05Li0.05O1‐δ is likely due to the localized nature of hopping charge carriers in addition to interfacial polarization due to space charge. Tm was found to increase with increasing frequencies suggesting the relaxor nature of dielectricity in the Zn0.9Cu0.05Li0.05O1‐δ. Bulk pristine Zn0.9Cu0.05Li0.05O1‐δ also exhibits ferroelectricity at room temperature with remnant polarization Pr and Vc equal to 4.20e–02 μC/cm2 and 4.1e+03 V/cm at (30KV, 500 Hz) respectively. Zn0.9Cu0.05Li0.05O also shows the paramagnetic behaviour.

Spin-orbit coupled spin-polarised hole gas at the CrSe2-terminated surface of AgCrSe2

In half-metallic systems, electronic conduction is mediated by a single spin species, offering enormous potential for spintronic devices. Here, using microscopic-area angle-resolved photoemission, we show that a spin-polarised two-dimensional hole gas is naturally realised in the polar magnetic semiconductor AgCrSe2 by an intrinsic self-doping at its CrSe2-terminated surface. Through comparison with first-principles calculations, we unveil a striking role of spin-orbit coupling for the surface hole gas, unlocked by both bulk and surface inversion symmetry breaking, suggesting routes for stabilising complex magnetic textures in the surface layer of AgCrSe2.

Room-temperature ferromagnetism in Fe-doped SnSe bulk single crystalline semiconductor

The quest for pragmatic room-temperature (RT) magnetic semiconductors (MSs) with a suitable bandgap constitutes one of the contemporary opportunities to be exploited. This may provide a materials platform for to bring new-generation ideal information device technologies into real-world applications where the otherwise conventionally separately utilized charge and spin are simultaneously exploited. Here we present RT ferromagnetism in an Fe-doped SnSe (Fe:SnSe) van der Waals (vdW) single crystalline ferromagnetic semiconductor (FMS) with a semiconducting bandgap of ∼1.19 eV (comparable to those of Si and GaAs). The synthesized Fe:SnSe single crystals feature a dilute Fe content of <1.0 at%, a Curie temperature of ∼310 K, a layered vdW structure nearly identical to that of pristine SnSe, and the absence of in-gap defect states. The Fe:SnSe vdW diluted magnetic semiconductor (DMS) single crystals are grown using a simple temperature-gradient melt-growth process, in which the magnetic Fe atom doping is realized uniquely using FeI2 as the dopant precursor whose melting point is low with respect to crystal growth, and which in principle possesses industrially unlimited scalability. Our work adds a new member in the family of long-searching RT magnetic semiconductors, and may establish a generalized strategy for large-volume production of related DMSs.

Two-dimensional transition metal halide PdX 2 (X = F, Cl, Br, I): A promising candidate of bipolar magnetic semiconductors

Two-dimensional (2D) nanomaterials with bipolar magnetism show great promise in spintronic applications. Manipulating carriers’ spin-polarized orientation in bipolar magnetic semiconductor (BMS) requires a gate voltage, but that is volatile. Recently, a new method has been proposed to solve the problem of volatility by introducing a ferroelectric gate with proper band alignment. In this paper, we predict that the PdX 2 (X = F, Cl, Br, I) monolayers are 2D ferromagnetic BMS with dynamic stability, thermal stability, and mechanical stability by first-principles calculations. The critical temperatures are higher than the boiling point of liquid nitrogen and the BMS characteristics are robust against external strains and electric fields for PdCl2 and PdBr2. Then, we manipulate the spin-polarization of PdCl2 and PdBr2 by introducing a ferroelectric gate to enable magnetic half-metal/semiconductor switching and spin-up/down polarization switching control. Two kinds of spin devices (multiferroic memory and spin filter) have been proposed to realize the spin-polarized directions of electrons. These results demonstrate that PdCl2 and PdBr2 with BMS characters can be widely used as a general material structure for spintronic devices.

Intrinsic bulk Ga0.50V0.50As magnetic semiconductor with optical transparency at room temperature

Searching for intrinsic magnetic semiconductors has long been pursued in the last few decades. Nonetheless, it failed to fabricate an intrinsic magnetic semiconductor at room temperature. Also, it is a challenging task to fabricate optically transparent magnetic material at room temperature. Here, we investigate the magnetic and optical properties of Ga1-xVxAs (x = 0.25, 0.5, and 0.75). We find that only the Ga0.50V0.50As structure meets all the structural stability criteria. The Ga0.50V0.50As has a ferromagnetic ground state with a Curie temperature of 478 K. The Ga0.50V0.50As has an indirect band gap of 1 eV, and also the majority spin bands locate at the conduction band minimum and valence band maximum. Thus, we can achieve 100 % spin-polarized current. Moreover, the Ga0.50V0.50As system displays optically transparent properties in the visible frequencies. Overall, we propose that the Ga0.50V0.50As can be a potential candidate as a magnetic semiconductor for transparent spintronics device applications.

The effect of biaxial strain on the electronic properties, quantum capacitance and diffusion of Li adsorption on Sc2CO2 MXene

Searching for high-performance electrode materials is an urgent need for lithium-ion batteries (LIBs) and supercapacitors. The electronic properties, quantum capacitance and diffusion of Li adsorption on Sc2CO2 under biaxial strain are investigated by density functional theory. Twelve adsorption sites are considered. The most stable adsorption site is confirmed through adsorption energy. The adsorption of Li makes Sc2CO2-Li monolayer become the magnetic semiconductor, with the maximum bandgap of 1.84 eV at −2 % strain and 0.76 eV at +4 % strain for spin-up and spin-down states, respectively. The maximum theoretical capacity of Sc2CO2 monolayer is 190.26 mAhg−1. The most appropriate diffusion path for Li atom is confirmed by analyzing diffusion barriers and Sc2CO2-Li monolayer under −4 % strain is more suitable as an anode material for LIBs because of the minimum open circuit voltage (OCV) and diffusion barrier. The coexistence of biaxial strain and Li adsorption doesn't change the cathode electrode type of Sc2CO2 monolayer. Charge transfer in Sc2CO2-Li monolayer under strain is further analyzed.

Tunable the electronic and magnetic properties of monolayer Mo8S12 via defects and 3d transition metal substitutional doping

The effect of vacancy defects and substitutional doping with 3d transition metal (TM) atoms (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) were comprehensively investigated on the structural, electronic and magnetic properties of monolayer Mo8S12 by first-principles calculations. It was discovered that the monolayer Mo8S12 systems with S-vacancies (V1S and V2S) are non-magnetic semiconductors. Surprisingly, the VMo1-, VMo2- and VMoS6-vacancies systems exhibit magnetism, and the magnetic moments are predominantly derived from the Mo atoms around these vacancies. Furthermore, the VMo1-system is a magnetic semiconductor, whereas the VMo2- and VMoS6- systems exhibit half-metal characteristics. For the substitution doping cases, the 3d TMs substituted doping at the TM-1(Mo-1) site in monolayer Mo8S12 results in magnetic semiconductors except for Cr and Fe atoms. Similarly, magnetic behavior is induced when dopants occupy the TM-2 (Mo-2) site except for Ti, Cr and Fe atoms. Furthermore, the half-metallic behavior can be found for Mn-Mo8S12 system. These theoretical findings demonstrate the feasibility of utilizing vacancy defects and substitutional doping to control the performance of monolayer Mo8S12, thereby offering important implications for the design and development of novel electronic and spintronic devices based on Mo8S12.

Optical Helicity and Polarization Dependent NIR Negative Photocurrent in the 2D Magnetic Semiconductor CrI3

AbstractTwo‐dimensional magnetic semiconductors provide a fascinating platform for studying magneto‐optoelectronic properties at the atomically thin limit and have potential in developing novel devices. In this paper, the superior negative photoconductivity (NPC) characteristics of graphene‐CrI3‐graphene van der Waals heterostructure in light detection, such as a broader detection range (650–1250 nm) and faster response time (&lt;0.32 ms), as well as light helicity and polarization sensitivity are reported. Under near‐infrared (NIR) light illumination, the NPC‐related photoresponsivity R and specific detectivity D* are 1.18 A W−1 and 1.26 × 109 Jones, respectively. Under magnetic field conditions, the NPC and positive photoconductivity (PPC) show opposite optical helicity dependence. The photoresponsivity helicity of the NPC‐dominated photocurrent can reach 16.01%. Besides, NPC and PPC show obvious and similar linear polarization dependence, independent of magnetic fields. It is demonstrated that NPC is superior to PPC in some aspects, such as fast detection of red and NIR lights as well as their helicity and polarization, especially in the NIR region. This work explores many unique phenomena of NPC, further revealing the interplay between magnetic and optoelectronic properties in CrI3, and paves the way for expanding traditional photoelectric detection and optical communication with higher data transmission rates.

Carriers induced ferromagnetism in Co(II)-doped ZnO monolayers and their optical properties: First principles calculations

Diluted magnetic semiconductors are advantageous for magneto-electronic devices because they create ferromagnetism at high Curie temperatures and exhibit spin-dependent interactions. The complex microstructural and compositional aspects of optical emission dynamics and ferromagnetism are still unknown. Here, using first-principles calculations, we investigate the magnetic and opto-electronic characteristics of Co(II) mono-doped and (Co, Na) co-doped ZnO monolayers. The results show that Na co-doping can change the ground state of a Co(II)-doped monolayer from AFM to FM due to the exchange coupling between the Co-d spins and hole produced by Na. The observed room-temperature (RT) ferromagnetism in the co-doped monolayer below with 5 % Na doping is due to exchange coupling via electron trapping oxygen vacancies with the magnetic Co ions. The optical investigation reveals a red shift in the d-band to d-band transition of Co(II) and a blue shift in the fundamental energy gap with increasing Co concentration. Na co-doping results in mid-IR and near-infrared absorption peaks. Furthermore, the correlation between spin-spin coupling and optical absorption shows that the FM(AFM) systems exhibit a red-shift (blue-shift) in the fundamental band gap energy and spin-allowed d-band to d-band transition of Co ions. The enhanced optical and magnetic findings suggest that the (Co, Na);ZnO monolayer might be a suitable option for spin-photonic and spintronic devices in the future.

A Density Functional Theory Study on Al2CO-Based Diluted Magnetic Semiconductor

A Density Functional Theory Study on Al2CO-Based Diluted Magnetic Semiconductor

First‐Principles Study of the C‐ and Si‐Doped Buckled Honeycomb PN Monolayer

AbstractIn this work, the effects of doping with carbon (C) and silicon (Si) on the electronic and magnetic properties of phosphorus nitride (PN) monolayer are investigated. PN monolayer is stable, exhibiting the semiconductor nature with indirect band gap of 1.81(2.89) eV calculated by standard Perdew–Burke–Ernzerhof (hybrid HSE06) functional. C and Si impurities prefer doping at N and P sublattices, respectively. PN monolayer is slightly magnetized by doping with 25% of C with total magnetic moment of 0.20 . The magnetization is stronger in the remaining cases with total magnetic moments of 1.00 . Magnetic properties are produced mainly by C and Si impurities. In addition, C and Si codoping is also investigated, in which the magnetization depends strongly on the interatomic distance between impurities. Specifically, the inter‐dopant interactions preserve the non‐magnetic nature of PN monolayer, but significantly reduce the energy gap. However, further separating these dopants leads to the emergence of magnetism with total magnetic moment of up to 1.97 . Results may introduce doping‐based effective method to induce feature‐rich electronic and magnetic properties in buckled honeycomb PN monolayer. Such that, the C‐ and Si‐doped PN sheets are recommended for spintronic applications considering their magnetic semiconductor nature.