Ferromagnetic Semiconductor Research Articles (Page 1)

Two-dimensional ferromagnetic semiconductors have attracted great attention due to their applications in the next generation of nanoscale spintronics. However, experimentally confirmed two-dimensional ferromagnetic semiconductors are rather limited and suffer from a rather low Curie temperature. Based on density functional theory, the structure, electronic, and magnetic properties of the CrCl3-xBrx (x = 0, 1, 2, 3) monolayers are systematically explored. As a result, they are all semiconductors with intrinsic ferromagnetism, and their band gaps decrease with increasing Br composition. Interestingly, due to the joint effects of spin-orbit coupling and magnetic dipole-dipole interaction, the magnetic easy axes have a transition from in-plane to out-of-plane with Br composition increasing. In addition, by the isovalent alloying method, the FM coupling of CrCl3-xBrx can be remarkably enhanced, and their Curie temperature can be increased to 120 K, 130 K, 145 K and 170 K without introducing any carriers, respectively. Besides, the CrCl3-xBrx monolayers have good thermal and dynamical stability, and their small exfoliation energies confirm that they can be exfoliated from the bulk flexibly. Our findings not only provide an effective method to improve ferromagnetism in 2D semiconductors but also provide a class of potential candidates for realistic spintronic applications.

Materials displaying ferroelectric and ferromagnetic properties offer a fascinating foundation for future spintronic innovations like multi-state random-access memory and data storage devices. Herein, numerous features of pristine and F@O-doped-PbO (PO)/TiO2 (TO)-layer PbTiO3 perovskite oxides are investigated via ab initio calculations. The calculated negative formation enthalpies and elastic coefficients verify the thermodynamic and mechanical stability of the structures, respectively. The pristine motif exhibits a giant spontaneous polarization (P) of 88 μC cm−2, having a non-magnetic insulating state with an indirect energy gap (Eg) of 2.11 eV. It appears that the dopant reduces the structural distortions, lowering P to 42.56/42.78 μC cm−2 in the F@O-doped PO/TO-layer-based structure. The most notable aspect of the present study is that F-doping in the PO layer induces an n-type half-metallic (HM) ferromagnetic (FM) behavior with a total magnetic moment (mt) of 1.0 μB. It is found that Ti ions are the main contributor to the magnetism, which is confirmed by spin-magnetization density isosurface plots. Additionally, a large Eg of 2.49 eV in the spin-minority channel is found, which is large enough to ensure the HM state and avoid reverse leakage current. Conversely, the F@O-doped TO-layer-based system transforms to an FM semiconductor with an Eg of 0.23 eV. Interestingly, the highest figure of merit of 0.72/0.56/0.49 is predicted at 700/700/400 K for the pristine/F@O-doped PO/TO-layer-based structures with the inclusion of lattice thermal conductivity. Thus, due to high structural stability, high P, half-metallicity, and low thermal conductivity, the F@O motif emerges as a promising candidate for various potential applications in spintronics and energy conversion.

We investigate current-induced spin–orbit fields (SOFs) in a bilayer heterostructure composed of a ferromagnetic semiconductor (Ga,Mn)As and a topological insulator (Bi2Te3). Planar Hall resistance (PHR) measurements at 3 K during field rotation reveal clear current polarity-dependent hysteresis shifts when the magnetization transitions involve a change perpendicular to the current direction, whereas no shifts are observed when the magnetization change is collinear to the current. This behavior confirms the presence of effective SOFs oriented perpendicular to the current direction. The magnitude of the hysteresis shift decreases with increasing external magnetic field, enabling quantitative extraction of SOF components using a magnetic free energy model. By analyzing PHR data for currents along [110] and [11¯0], we separately determine the Dresselhaus- and the net Rashba-type SOFs, with the latter including contributions from both (Ga,Mn)As and the Bi2Te3 surface states. The net Rashba-type SOF is found to be negative, demonstrating that the SOF contribution from the Bi2Te3 surface states opposes and outweighs that of intrinsic Rashba-type SOF in (Ga,Mn)As. These findings provide direct evidence that topological surface states significantly tune current-induced SOFs in FMS/TI bilayers, offering a promising route toward efficient, all-electrical spintronic devices.

Motivated by the seminal discoveries in graphene, the exploration of novel physical phenomena in alternative two-dimensional (2D) materials has attracted tremendous attention. In this work, through theoretical investigation using first-principles calculations, we reveal that Mo-intercalated bilayer exhibits ferromagnetic semiconductor behavior with a small easy-plane magnetocrystalline anisotropy energy (MAE) of 0.618 meV/Cr(Mo) between (100) and (001) magnetizations. The spin–orbit coupling (SOC) opens a narrow band gap at the Fermi level for both magnetization orientations with nonzero Chern number for realizing the quantum anomalous Hall effect (QAHE) in the former and with trivial topology in the latter. The small MAE implies the efficient experimental manipulation of magnetization between distinct topologies through an external magnetic field. Our findings provide compelling evidence that the QAHE in this system originates from the quantum spin Hall effect (QSHE), driven by intrinsic magnetism under broken time-reversal symmetry. These unique properties position Mo-intercalated as a promising candidate for tunable spintronic applications.

Two-dimensional single-phase magnetoelectric multiferroic semiconductors are attractive for the multifunctional spintronic nanodevices due to their cross coupling between coexisting magnetic and ferroelectric orders. However, experimentally synthesized two-dimensional magnetoelectric multiferroic materials are very rare to date because of the mutual exclusion between ferroelectricity and magnetism. Here, we predict a two-dimensional room-temperature ferromagnetic multiferroic Ti2F3 semiconductor through the first-principles calculations and Monte Carlo simulations. The Ti2F3 monolayer manifests an easy magnetization plane, and the magnitude of the out-of-plane polarization is 0.037 C/m2. Interestingly, the magnetic ground states of the Ti2F3 monolayer can be tuned by the electric field. Moreover, we explore the electric field tunable magneto-optical effects in the Ti2F3 monolayer. Our work provides more magnetoelectric multiferroic candidate materials and suggests an effective strategy to realize and probe the magnetic phase transition.

Ductile/Plastic inorganic semiconductors have garnered significant attention for their potential in flexible electronics, yet their current diversity remains limited, with functionalities largely confined to thermal and/or electrical properties. Here, the first intrinsically ductile/plastic inorganic ferromagnetic semiconductor, bulk CrSiTe3 van der Waals (vdW) crystals, which combine excellent deformability with ferromagnetism, is reported. Mechanical characterization reveals excellent plasticity at room temperature, with CrSiTe3 crystals sustaining up to 12% tensile strain, surpassing many existing plastic bulk vdW semiconductors. Below the Curie temperature of 34K, the material retains ferromagnetic ordering, with plasticity exerting negligible effects on Curie temperature or saturation magnetization. First-principles calculations attribute the exceptional deformability to low interlayer slip energy barriers and high cleavage energy within Te-terminated vdW layers, enabling interlayer gliding without fracture. Monte Carlo simulations confirm that interlayer slip minimally perturbs magnetic interactions, preserving ferromagnetism. This work bridges the gap between mechanical plasticity, semiconductivity, and ferromagnetism in a single material, extending the functionality of plastic inorganic semiconductors.

Two-dimensional (2D) van der Waals (vdW) magnetic semiconductors are a new class of quantum materials for studying the emergent physics of excitons and spins in the 2D limit. Twist engineering provides a powerful tool to manipulate the fundamental properties of 2D vdW materials. Here, we show that twist engineering of the anisotropic ferromagnetic monolayer semiconductor CrSBr leads to bilayer magnetic semiconductors with continuously tunable magnetic moment, dielectric anisotropy, exciton energy, and linear dichroism. We furthermore provide a model for exciton energy in the media with tunable anisotropy. These results advance fundamental studies of 2D vdW materials and open doors to applications to nano-optics, twistronics, and spintronics.

Intrinsic ferromagnetism, with coexisting ferroelectric and ferrovalley polarizations in a single two-dimensional semiconductor, is highly desirable for developing next-generation multifunctional nanospintronic devices. Based on first-principles calculations and Monte Carlo simulations, the two-dimensional V2N2O monolayer is predicted to be an indirect bandgap ferromagnetic semiconductor, characterized by a near-room-temperature Curie temperature and an out-of-plane easily magnetized axis. Interestingly, the spontaneous valley polarization can be effectively modulated by the ferroelectric polarization. Remarkably, the anomalous valley Hall effect in the V2N2O monolayer can be controlled by reversing the magnetization. Thus, the V2N2O monolayer is considered a potential candidate for polymorphic memory and multifunctional valley electronic devices.

2D ferromagnetic semiconductors are recognized as the cornerstone of next-generation spintronics devices. However, their practical applications are severely hindered by the low Curie temperature, which originates from the weak d-p-d ferromagnetic superexchange interaction. H- anion with short ionic radius can effectively shorten the distance between magnetic centers and simultaneously induce a perfect 180° superexchange angle to strengthen the magnetic coupling, thus achieving high-temperature magnetic ordering. Here, by first-principles calculations, such a case in 2D Ruddlesden-Popper phase hydride double perovskite A4NiVH8 (A = Na, K, Rb) is demonstrated. These hydride monolayers possess quite good thermodynamic stability and can retain their structures under normal pressure at least at 500 K. Magnetic and electronic properties calculations reveal that they are all ferromagnetic semiconductors with high Curie temperatures (up to 429 K) and superior electron mobilities (up to 5522 cm2 V-1 s-1, based on the deformation potential theory). In addition, monolayer Na4NiVH8 exhibits the characteristics of a bipolar magnetic semiconductor with gate-tunable spin polarization.

We introduce a novel two-dimensional ferromagnetic valley material, TiSeCl, and confirm its potential to enable valley-related multichannel Hall effects within a stable two-dimensional ferromagnetic semiconductor. The intrinsic lack of spatial inversion symmetry and time-reversal symmetry in the TiSeCl structure allows for spontaneous valley polarization, making it highly advantageous for practical valley manipulation since its intrinsic valley polarization values can reach 95meV. The strong spin-orbit coupling effects in the TiSeCl monolayer result in distinct Berry curvatures and opposing signals in the +K and -K valleys, leading to an anomalous valley Hall effect. Furthermore, under a 1.25% tensile strain, the TiSeCl monolayer undergoes band inversion, leading to a topological phase transition from the ferromagnetic valley state to the semivalley metal state and subsequently to a valley-polarized quantum anomalous Hall phase. This study expands our understanding of valley properties in two-dimensional materials and provides theoretical guidance for valley manipulation in valley electronics.

Owing to their distinctive thickness and physical attributes, two-dimensional (2D) materials have exhibited considerable promise in the field of microelectronic devices. Notably, 2D magnetic materials that maintain long-range magnetic order and can be readily modulated by external fields have garnered substantial attention. However, CrSBr, despite being a 2D van der Waals (vdW) semiconducting magnet with an appropriate band gap and stability in air, faces significant hindrance for practical utilization due to its Curie temperature (TC) of 146 K. The construction of vdW heterostructures through coupling represents an effective approach to improving the intrinsic properties of 2D materials. In this research, 2D elemental ferroelectric Bi (110), which comprises heavy elements, is selected to construct a vdW heterostructure with a CrSBr monolayer. The difference in work function results in interfacial charge transfer from the Bi layer to the CrSBr layer. The CrSBr/Bi heterostructure demonstrates ferromagnetic semiconductor characteristics, exhibiting significant interface orbital coupling between Bi-p and Cr-d. Additionally, it introduces a new super-exchange pathway, Cr-Bi-Cr, to the intrinsic Cr-S/Br-Cr, which increases the TC to 340 K. The CrSBr/Bi heterostructure possesses robust perpendicular magnetic anisotropy without destroying the ferroelectric behavior of the Bi layer (-0.026 × 10-10 C m-1). These results provide a new design platform and research ideas for the development and application of room-temperature spintronic devices.

High Curie temperature and excellent spin transport properties in one-dimensional ferromagnetic semiconductors CrS3 and CrS2Se

The discovery of two-dimensional (2D) ferromagnetic semiconductors holds significant promise for advancing Moore's law and spintronics in-memory computing, sparking tremendous interest. However, the Curie temperature of explored 2D ferromagnetic semiconductors is much lower than room temperature. Although plenty of 2D room-temperature ferromagnetic semiconductors have been theoretically predicted, there have been formidable challenges in preparing such metastable materials with ordered structures and high stability. Here, utilizing a novel template-assisted chemical vapor deposition strategy, we synthesized layered MnS2 microstructures within a ReS2 template. The high-resolution atomic structure representation revealed that monolayer MnS2 microstructures well crystallize into a distorted T-phase. Room-temperature ferromagnetism was confirmed through vibrating sample magnetometer measurements, microzone magnetism imaging techniques, and transport characterization. Theoretical calculations indicated that the room-temperature ferromagnetism originates from the Mn-Mn short-range interaction. Our observation not only offered the experimental confirmation of the intrinsic room-temperature ferromagnetism in layered MnS2, but also provided an innovative strategy for the growth of 2D metastable functional materials.

Controlling two-dimensional (2D) valleytronics is challenging for information technology. This study shows that a ferroelectric-assisted layer can effectively enable non-volatile control of 2D valleytronics. Using first-principles simulations, we find that different polarization states in the Sc2CO2 layer cause the RuBrF monolayer to transition from a semiconductor to a half-metal, while also changing magnetic anisotropy from in-plane to out-of-plane. In the −P state, the system behaves as a ferromagnetic semiconductor with a spontaneous valley polarization of 329 meV. In the +P state, it becomes a ferromagnetic half-metal, blocking valleytronics. This enables electro-reversible control of valley electrons in the RuBrF/Sc2CO2 heterostructure. We explain the modulation of magnetic anisotropy and valley polarization using second-order perturbation theory and the k⋅p model. Our work offers a promising approach for non-volatile valleytronic control at the nanoscale, aiding the design of new devices.

Unraveling the microscopic origin of out of plane magnetic anisotropy in VI3

The study investigated how out-of-plane structural inversion asymmetry (SIA) influences current induced spin–orbit fields (SOFs) in crystalline (Ga,Mn)As ferromagnetic films. By growing (Ga,Mn)As films in which the manganese composition is gradually increased or decreased along the growth direction of the film, we systematically control the out-of-plane SIA in the films. Using Hall measurements designed to probe current-induced SOFs, we identify both Dresselhaus-type SOF, arising from bulk inversion asymmetry, and the Rashba-type SOF, originating from SIA of the films. While the sign of the Dresselhaus-type SOFs remains unchanged regardless of the out-of-plane asymmetry direction (i.e., ascending or descending order variation of Mn composition in the film), the Rashba-type SOFs exhibit opposite orientations depending on the Mn gradient along the growth direction. These results provide direct experimental evidence of out-of-plane SIA-driven Rashba-type SOF modulation and establish a robust platform for engineering spin–orbit torque phenomena in ferromagnetic semiconductor systems.

Abstract The emerging class of two-dimensional piezoelectric ferromagnetic (PFM) systems, combining intrinsic ferromagnetism and piezoelectricity, has attracted significant attention for their potential in multifunctional spintronic devices. In this work, we systematically investigate the electronic structure, magnetic properties, and piezoelectric performance of Janus MoTeX (X = Cl, Br, I) monolayers using first-principles calculations and Monte Carlo simulations. Our results demonstrate that these MoTeX monolayers are stable intrinsic ferromagnetic semiconductors. The Janus-structured MoTeCl, MoTeBr, and MoTeI monolayers exhibit out-of-plane piezoelectric coefficients (d 31) of 1.42, 1.08, and 0.50 pm V−1, respectively, surpassing most reported 2D materials. This enhanced piezoelectricity originates from the broken inversion symmetry along the vertical direction. Notably, MoTeCl, MoTeBr, and MoTeI monolayers display high Curie temperatures (T c ), with values of 190, 219, and 249 K. Furthermore, Janus MoTeX monolayers exhibit excellent mechanical flexibility. The application of biaxial tensile strain engineering significantly improves the PFM performance of MoTeCl monolayers: a 2% strain elevates T c to room temperature and induces a transition of the easy magnetization axis from in-plane to out-of-plane, substantially enhancing their practical applicability. These findings highlight Janus MoTeX monolayers as promising candidates for developing next-generation multifunctional spintronic devices.

Abstract Realizing ferromagnetic semiconductors with high Curie temperature T C is still a challenge in spintronics. Recent experiments have reported two-dimensional (2D) room temperature ferromagnetic metals, such as monolayer Cr3Te6. In this paper, by the density functional theory (DFT) calculations, we proposed a way to obtain 2D high T C ferromagnetic semiconductors through element replacement in these ferromagnetic metals. We predict that monolayer (Cr4/6, Mo2/6)3Te6, created via element replacement in monolayer Cr3Te6, is a room-temperature ferromagnetic semiconductor exhibiting a band gap of 0.34 eV and a T C of 384 K. Our analysis reveals that the metal-to-semiconductor transition stems from the synergistic interplay of Mo-induced lattice distortion, which resolves band overlap, and the electronic contributions of Mo dopants, which further drive the formation of a distinct band gap. The origin of the high T C is traced to strong superexchange coupling between magnetic ions, analyzed via the superexchange model with DFT and Wannier function calculations. Considering the fast developments in fabrication and manipulation of 2D materials, our theoretical results propose a way to explore the high temperature ferromagnetic semiconductors from experimentally obtained 2D high temperature ferromagnetic metals through element replacement.

Abstract Two-dimensional (2D) layered ferromagnets offer exciting opportunities for studying magnetic phenomena and developing advanced spintronic devices. In this study, we experimentally present a 2D chromium indium telluride (Cr6In2Te12, CIT) that exhibits robust room-temperature ferromagnetism and remarkable magnetic properties.CIT demonstrates a high Curie temperature of 320 K, record-high room-temperature saturation magnetization (~52.3 emu/g), and a strong magnetocaloric effect. Notably, with decreasing thickness, it transitions from a metallic ferromagnet to a ferromagnetic semiconductor. Besides, CIT displays complex magnetocrystalline anisotropy with multiple easy axes and signatures of an abnormal phase transition, characterized by anisotropic anomalies in field- and temperature-dependent magnetization curves. Furthermore, CIT shows anisotropic magnetic interactions and critical exponents consistent with a mean-field model. These exceptional properties position CIT as a promising 2D high-TC ferromagnetic semiconductor for multidisciplinary applications, particularly in high-performance spintronic devices.

This study explores the mechanisms of spin–orbit torque (SOT) switching in ferromagnetic semiconductors (FMS) with perpendicular magnetic anisotropy (PMA), emphasizing the impact of symmetry-breaking. Using micromagnetic simulations based on the Landau-Lifshitz-Gilbert (LLG) equation, we examine several symmetry-breaking factors, including bias field misalignment, interlayer exchange coupling, out-of-plane spin polarization, and tilted magnetic anisotropy. The results reveal that bias field misalignment relative to the film plane significantly distorts the SOT switching hysteresis. Additionally, intrinsic symmetry-breaking effects, such as internal coupling fields, out-of-plane spin polarization, and tilted anisotropy, facilitate field-free SOT (FF-SOT) switching without external bias fields. Each type of FF-SOT switching exhibits distinct characteristics, including hysteresis shifts, switching ratios, and saturated magnetization. The combine effects, such as interlayer exchange bias and tilted anisotropy, significantly change the switching current density depending on their constructive or destructive combination in a device. Furthermore, a new approach to symmetry breaking via the Oersted field is proposed, which is applicable only along the ⟨100⟩ crystallographic directions of the FMS. This work emphasizes the role of symmetry-breaking in FF-SOT switching and offers fundamental information for interpreting FF-SOT switching observed from FMS films in experiments, contributing to the optimization of SOT efficiency and the advancement of spintronics technologies.