Magnetic Semiconductors Research Articles

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 (<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.

Broadband unidirectional surface plasmon polaritons with low loss.

Unidirectional surface plasmon polaritons (SPPs) have been proven to truly exist at an interface between a magnetized semiconductor and an opaque isotropic material, however, they suffer rather serious leakage loss (with propagation length shorter than two wavelengths) caused by nonlocality. In this work, we investigate an alternative category of unidirectional SPPs existing on a nonreciprocal plasmonic platform with a cladding composed of a dielectric heterostructure transversely terminated by metal. This unidirectional SPP mode exists for small wavenumbers within the entire upper bulk-mode bandgap of the magnetized semiconductor, hence it is robust against nonlocal effects over a broad band. In contrast to previous unidirectional SPPs, the leakage loss of the present unidirectional SPPs is significantly reduced by more than five times, since the portion of modal energy distributed in the cladding is substantially increased. A similar reduction in absorption losses associated with semiconductor dissipation is observed. Though the nonlocality induces a backward-propagating SPP with extremely large wavenumbers, it can be suppressed even at very small level of dissipation. Therefore, our proposed plasmonic waveguide actually exhibits exceptional unidirectional characteristics.

Strain-controlled spin transport in a two-dimensional (2D) nanomagnet

Semiconductors with controllable electronic transport coupled with magnetic behaviour, offering programmable spin arrangements present enticing potential for next generation intelligent technologies. Integrating and linking these two properties has been a long standing challenge for material researchers. Recent discoveries in two-dimensional (2D) magnet shows an ability to tune and control the electronic and magnetic phases at ambient temperature. Here, we illustrate controlled spin transport within the magnetic phase of the 2D semiconductor CrOBr and reveal a substantial connection between its magnetic order and charge carriers. First, we systematically analyse the strain-induced electronic behaviour of 2D CrOBr using density functional theory calculations. Our study demonstrates the phase transition from a magnetic semiconductor → half metal → magnetic metal in the material under strain application, creating intriguing spin-resolved conductance with 100% spin polarisation and spin-injection efficiency. Additionally, the spin-polarised current–voltage (I–V) trend displayed conductance variations with high strain-assisted tunability and a peak-to-valley ratio as well as switching efficiency. Our study reveals that CrOBr can exhibit highly anisotropic behaviour with perfect spin filtering, offering new implications for strain engineered magneto-electronic devices.

Chemically Controlled Reversible Magnetic Phase Transition in Two-Dimensional Organometallic Lattices.

Developing an efficient method to reversibly control materials' spin order is urgently needed but challenging in spintronics. Though various physical field control methods have been advancing, the chemical control of spin is little exploited. Here, we propose a chemical means for such spin manipulation, i.e., utilizing the well-known lactim-lactam tautomerization to reversibly modulate the magnetic phase transition in two-dimensional (2D) organometallic lattices. The proposal is verified by theoretically designing several 2D organometallic frameworks with antiferromagnetic to ferrimagnetic spin order transformation modulated by lactim-lactam tautomerization on organic linkers. The transition originates from the change in spin states of organic linkers (from singlet to doublet) via tautomerization. Such a transition further switches materials' electronic structures from normal semiconductors with zero spin polarization to bipolar magnetic semiconductors with valence and conduction band edges 100% spin polarized in opposite spin channels. Moreover, the magnitude of magnetic anisotropy energy also enhances by 5- to 9-fold.

Recent progress in diluted ferromagnetism for spintronic application

With the continuous in-depth research of spintronics, the manufacture of high-performance magnetic random access memory devices and electronic devices that are more energy-efficient and generate less heat has received extensive attention. The traditional ferromagnet TbMnO3 is basically Tc at room temperature, which seriously limits its application. Since the discovery of diluted magnetic semiconductor materials at room temperature, such as AlNTiO2, ZnO, SnO2, etc., they have received increasing attention. Although these dopants can form ferromagnetism above-room temperature, the ferromagnetic mechanism and ferromagnetic properties are different. In this regard, we reviewed the current progress in the research on above room temperature dilute magnetic semiconductor materials; discussed the ferromagnetic mechanism of dilute magnetic semiconductors; summarized the problems and challenges, and advantages and disadvantages of different kinds of dilute magnetic semiconductor materials used in new memory devices; and prospected the application potential of spintronic devices.

Magnetic ground state of holmium nitride

Rare-earth mononitrides such as HoN exhibit a wide range of useful properties leading to potential applications as magnetic semiconductors, spintronic half-metals, or magnetocaloric refrigerants in hydrogen liquefaction systems. First-principle calculations of electronic structures and related properties of such materials should correctly reproduce their magnetic moment. First, we identify the unusually high number of unoccupied electronic states which guarantees that the energy minimum identified is the global one. Second, we develop a method which allows the experimentally relevant magnetisation to constitute an energy minimum, emphasising the favourable distribution of the spins in an exceptionally large simulation cell. Third, we examine the dependence of selected HoN characteristics on the cell size and on the magnetisation. The results provide a theoretical insight into the spin structure of rare-earth nitrides and allow one to use the correct methodology of similar calculations of properties of strongly correlated materials.

Control of band polarity in two-dimensional VX2 (X = S, Se, and Te)

Bipolar magnetic semiconductor (BMS) has special electronic structures; i.e., its conduction band minimum (CBM) and valence band maximum (VBM) are completely spin-polarized in opposite directions. In this work, the band structures of 2H-VX2 (X = S, Se, and Te) are examined through first-principles calculations, and the results show that both 2H-VS2 and 2H-VSe2 are BMSs, while 2H-VTe2 is a unipolar magnetic semiconductor (UMS); i.e., its CBM and VBM show the same spin direction. Most interestingly, we find that electronic orbitals near the Fermi level of 2H-VX2 are occupied by dz2 and dxy orbitals, which can be effectively modulated by the biaxial strain. With appropriate strain modulations, 2H-VX2 can be BMS, UMS, or half-metal (HM). Our investigation reveals strain effects on the band structure of 2H-VX2, which greatly enhances their significance in spintronics.

Comprehensive study of Cesium-Tantalum Oxide for electronic, optical and thermoelectric properties under the effect of pressure for energy applications

The perovskites are important class of materials which are utilized for memory as well as spintronic devices. The thermoelectric response calculations for some perovskite oxides are also reported but their attributes under pressure had not really been touched. This study covers the repercussions of pressure on structure, electronic dispersions, optical constants and transport parameters of CsTaO3 perovskite oxides in cubic phase by employing semi-classical Boltzmann theory. The CsTaO3 was previously reported dynamically stable through optimization of energy against volume and phonon properties at ambient pressure conditions, having wide (direct) energy gap of 2.90 eV. This gap is decreasing with increasing pressure and behaves like the interesting diluted magnetic semiconductors. The comprehensive insights of the imaginary part of dielectric constant is predicting it’s utility in optoelectronic devices and sensors. The different transport parameters are computed in the temperature range 50 K to 1200 K with 50 K step size and pressure 0–100 GPa with 10 GPa step. The calculated power factor value and optical parameter proving CsTaO3 as a latent material for energy application.

A first-principles investigation on the structural, stability and mechanical properties of novel Ag, Au and Cu-graphdiyne magnetic semiconducting monolayers

Most recently, silver-metalated graphdiyne (GDY) nanomembranes have been fabricated using the wet-chemistry approach, with highly efficient response for light-driven decomposition of antibiotics (ACS Appl. Nano Mater. 2023, 6, 7395). Inspired by this exciting advance, herein for the first time we theoretically explore the key physical properties of the single-layer M-(N)GDY (M=Cu, Ag, Au) monolayers. Spin-polarized density functional theory (DFT) results reveal that metalated GDY monolayers favor a high-spin ground state, presenting a magnetic moment of 3 µB/unitcell. The sheets are characterized as small band gap magnetic semiconductors, ranging between 0.112 and 0.960 eV, in which only one spin contributes to the band gap. Ab-initio molecular dynamics results confirm the remarkable thermal stability of the constructed graphdiyne nanomembranes at 1000 K. The dynamical stability and mechanical properties at the ground state are furthermore investigated using machine learning interatomic potentials. The ultimate tensile strengths of the metalated graphdiyne lattices are found to be decent, over 6 GPa close to the ground state, but a few folds lower than the native metal-free counterparts. The presented first-principles results confirm remarkable thermal, dynamical and mechanical stability, and appealing electronic characteristics of the metalated graphdiyne nanosheets, attractive to design advanced light-weight energy storage/conversion and spintronic nanosystems.

Proximity-Induced Interfacial Room-Temperature Ferromagnetism in Semiconducting Fe3GeTe2.

The discoveries of two-dimensional ferromagnetism and magnetic semiconductors highly enrich the magnetic material family for constructing spin-based electronic devices, but with an acknowledged challenge that the Curie temperature (Tc) is usually far below room temperature. Many efforts such as voltage control and magnetic ion doping are currently underway to enhance the functional temperature, in which the involvement of additional electrodes or extra magnetic ions limits their application in practical devices. Here we demonstrate that the magnetic proximity, a robust effect but with elusive mechanisms, can induce room-temperature ferromagnetism at the interface between sputtered Pt and semiconducting Fe3GeTe2, both of which do not show ferromagnetism at 300 K. The independent electrical and magnetization measurements, structure analysis, and control samples with Ta highlighting the role of Pt confirm that the ferromagnetism with the Tc of above 400 K arises from the Fe3GeTe2/Pt interfaces, rather than Fe aggregation or other artificial effects. Moreover, contrary to conventional ferromagnet/Pt structures, the spin current generated by the Pt layer is enhanced more than two times at the Fe3GeTe2/Pt interfaces, indicating the potential applications of the unique proximity effect in building highly efficient spintronic devices. These results may pave a new avenue to create room-temperature functional spin devices based on low-Tc materials and provide clear evidence of magnetic proximity effects by using nonferromagnetic materials.

Synthesis and elucidation of structural, optical, vibrational and magnetic properties of Mn-doped V2O5 dilute magnetic semiconductor nanocrystals

Undoped and Mn-doped (5% and 10%) V2O5 nanocrystals have been synthesized by the chemical co-precipitation process followed by heating of the chemically obtained materials at 600°C. X-ray diffractometry, transmission electron microscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy, UV–visible absorption spectroscopy, photoluminescence spectroscopy, vibrating sample magnetometry and electron spin resonance spectroscopy have been used for material characterization. Williamson-Hall analyses revealed higher crystallite size but lower lattice strain, lattice stress and energy density of the Mn-doped V2O5 nanocrystals as compared to undoped ones. The vibrational properties were found to be influenced by the presence of Mn ions while photoluminescence results suggested the presence of vanadium vacancy and vanadium interstitial defects in the nanocrystals. The undoped V2O5 nanocrystals exhibited weak room-temperature ferromagnetic behaviour that got significantly stronger after Mn doping. The dilute magnetic semiconductor Mn-doped V2O5 nanocrystals are promising materials for applications in spintronics devices.

Electronic Structure and Magnetic Anisotropy Response of Janus Monolayer VSeTe

Herein, the electronic and magnetic properties of the 2D Janus monolayer VSeTe are computed based on first‐principles calculations. The structure stability plays a crucial role in real application for magnetic devices; it is found that the VSeTe favors 2H structure due to non‐negative frequencies in the phonon spectra. The VSeTe monolayer possesses a semiconductor nature with a bandgap of 1.03 eV (0.85 eV) for spin‐up (down) channels. Interestingly, it is shown in the computed results that VSeTe monolayer is a magnetic semiconductor with a magnetic moment of 1.00 . Additionally, the realization of magnetic anisotropy energy can pave the way to utilize VSeTe monolayer for applications in magnetic semiconductor devices.

Discovery of new potential magnetic semiconductors in quaternary Heusler compounds by addition of lanthanides

Magnetic semiconductors have attracted a lot of attention by having both electronic charge and spin degrees of freedom. In this paper, we obtained twenty magnetic semiconductors such as FeVLaSb, FeVPrSb, FeCrTbSi, CoVDySi, and CoVHoSi by adding lanthanides to quaternary Heusler compounds based on the Slater–Pauling law and orbital hybridization theory. The relationship between the lattice constants and energy gaps of the magnetic semiconductors with lanthanide elements is investigated by in-depth analysis. These magnetic semiconductors of quaternary Heusler compounds are promising candidates to find applications as spin filtering materials in spintronics devices.

Phase Engineering of 2D Spinel-Type Manganese Oxides.

2D magnetic materials have been of interest due to their unique long-range magnetic ordering in the low-dimensional regime and potential applications in spintronics. Currently, most studies are focused on strippable van der Waals magnetic materials with layered structures, which typically suffer from a poor stability and scarce species. Spinel oxides have a good environmental stability and rich magnetic properties. However, the isotropic bonding and close-packed nonlayered crystal structure make their 2D growth challenging, let alone the phase engineering. Herein, a phase-controllable synthesis of 2D single-crystalline spinel-type oxides is reported. Using the van der Waals epitaxy strategy, the thicknesses of the obtained tetragonal and hexagonal manganese oxide (Mn3 O4 ) nanosheets can be tuned down to 7.1nm and one unit cell (0.7nm), respectively. The magnetic properties of these two phases are evaluated using vibrating-sample magnetometry and first-principle calculations. Both structures exhibit a Curie temperature of 48 K. Owing to its ultrathin geometry, the Mn3 O4 nanosheet exhibits a superior ultraviolet detection performance with an ultralow noise power density of 0.126 pA Hz-1/2 . This study broadens the range of 2D magnetic semiconductors and highlights their potential applications in future information devices.