Two-dimensional Ferromagnetic Materials Research Articles

Magnetic properties of ferromagnetic nanoparticles of Fe x GeTe2 (x = 3, 5) directly exfoliated and dispersed in pure water

Fe x GeTe2 (x = 3, 5) are two-dimensional ferromagnetic (FM) materials that have gained significant attention from researchers due to their relatively high Curie temperature and tunability. However, the methods for preparing FM nanoparticles (FNPs) and large-area Fe x GeTe2 films are still in the early stages. Here, we studied the magnetic properties of Fe x GeTe2 FNPs exfoliated via wet exfoliation in pure water. The coercive field of Fe3GeTe2 FNPs increases significantly, up to 60 times, while that of Fe5GeTe2 only slightly increases from that of bulk crystals. Further investigation related to the dimension of nanoparticles and the Henkel plot analysis reveals that the variation in their coercive field stems from the material’s thickness-dependent coercive field and the type of term that governs the interaction between single-domain nanoparticles. Our work demonstrates a facile method for preparing FNPs using van der Waals FM materials and tuning their magnetic properties.

Impact of dimensionality on the magnetocaloric effect in two-dimensional magnets

Magnetocaloric materials, which exploit reversible temperature changes induced by magnetic field variations, are promising for advancing energy-efficient cooling technologies. The potential integration of two-dimensional materials into magnetocaloric systems represents an emerging opportunity to enhance the magnetocaloric cooling efficiency. In this study, we use atomistic spin dynamics simulations based on first-principles parameters to systematically evaluate how magnetocaloric properties transition from three-dimensional (3D) to two-dimensional (2D) ferromagnetic materials. We find that 2D features such as reduced Curie temperature, sharper magnetic transition, and higher magnetic susceptibility are beneficial for magnetocaloric applications, while the relatively higher lattice heat capacity in 2D can compromise achievable adiabatic temperature changes. We further propose GdSi2 as a promising 2D magnetocaloric material. Our calculation predicts that GdSi2 exhibits an isothermal entropy change ΔSM of 22.5 J kg−1 K−1 and an adiabatic temperature change ΔTad of 6.2 K, near the hydrogen liquefaction temperature (TC≈25 K). Our analysis offers valuable theoretical insights into the magnetocaloric effect in 2D ferromagnets and demonstrates that 2D ferromagnets hold promise for cooling and thermal management applications in compact and miniaturized nanodevices.

Two-dimensional intrinsic ferromagnetic materials of Janus 2H-NbXY (X, Y = S, Se and Te, X ≠ Y) monolayers with high Curie temperature and large magnetic anisotropy

Two-dimensional (2D) intrinsic ferromagnetic materials with large magnetic anisotropy (MA) and high Curie temperature (TC) are desirable for low-dimensional spintronic applications. In this work, a highly stable Janus NbXY (X, Y = S, Se and Te, X ≠ Y) monolayers with intrinsic ferromagnetism is investigated by using first-principles calculations. The results demonstrate that the MAE values of the NbSSe, NbSTe and NbSeTe MLs are as high as −2.185 meV, −4.013 meV and −4.495 meV per unit cell, respectively, which is higher than the previously reported 2D intrinsic ferromagnetic materials such as FeBrI, NiI2, and VSSe MLs etc. And they are still large enough for practical applications. The Curie temperature (Tc) is estimated to be 160 K for NbSSe monolayer, 260 K for NbSTe monolayer, and 200 K for NbSeTe monolayer based on Monte Carlo simulation. The MAE and Tc could be effectively controlled and enhanced by the biaxial strains. The MAE of NbSSe, NbSTe and NbSeTe MLs can be increased by 8.7%, 24.9% and 14.1%, and reach up to −2.375, −5.015 and −5.131 meV at 5% compressive strain, respectively. Remarkably, at 5% tensile strain, the room temperature Tc of 300 K can be reached for NbSTe monolayer, which is rather promising for its practical application. The large magnetic anisotropy energy and controllable Curie temperature make the NbXY monolayers a promising candidate for applications in spintronic devices at the nanoscale and in high-density data storage.

Robust Ferromagnetism in Hexagonal Honeycomb Transition Metal Nitride Monolayer.

Two-dimensional intrinsic magnetic materials with high Curie temperature are promising candidates for next-generation spintronic devices. In this work, we design two kinds of two-dimensional transition metal nitrides, VN2 and FeN2, both with a hexagonal honeycomb lattice. Based on the formation energy, and phonon spectra calculations as well as the molecular dynamics simulations, their structural stability is demonstrated. Then, we determine the ferromagnetic ground states of VN2 and FeN2 monolayers through the energy calculations, and the Curie temperatures of 222 K and 238 K are estimated by solving the Heisenberg model using the Monte Carlo simulation method. Hence, the VN2 and FeN2 monolayers are demonstrated to be new two-dimensional ferromagnetic materials with high temperature ferromagnetism or large-gap half-metallicity.

Half-metal Mn2GeI2 monolayer with high Curie temperature and large perpendicular magnetic anisotropy

Two-dimensional (2D) intrinsic ferromagnetic (FM) materials with high Curie temperatures (Tc), large perpendicular magnetic anisotropy (PMA), and large spin polarization are desirable for atomically thin spintronic devices. Herein, we propose a 2D intrinsic FM material Mn2GeI2 monolayer with thermodynamical stability and outstanding FM properties using first-principles calculations. Our calculations show that Mn2GeI2 monolayer is a half-metal with a spin gap of 1.76 eV, which ensures 100% spin polarization ratio at the Fermi level. Importantly, Mn2GeI2 monolayer has a large PMA energy of 2.90 meV and a high Tc of 648 K, ideal for practical applications at room temperature. Further in-depth investigation of microscopic coupling in the Mn2GeI2 monolayer reveals that the robust ferromagnetism mainly resulted from the synthetic effect of Ruderman–Kittel–Kasuya–Yosida exchange interaction between the Mn ion layers and superexchange interaction within the Mn ion layers. Our results give insights into the structure and electronic and magnetic properties of Mn2GeI2 monolayer and provide a promising candidate for 2D spintronic devices.

Design of 2D half-metallic [formula omitted] with robust ferromagnetism and high Curie temperature

Two-dimensional 2D ferromagnetic materials featuring intrinsic half-metallicity (HM) and high critical temperature Tc emerge as promising candidates for innovative low-dimensional spintronic devices. In this study, we employ first-principles calculations to predict a novel 2D half-metallic ferromagnet CoAl2S4 monolayer, a member of the layered AB2X4 family. The material’s energetic, mechanical, and dynamical stability is affirmed through analyses of its cohesive energy, elastic constants, and phonon spectrum, respectively. The ferromagnetic behavior observed in CoAl2S4 can be explained by the superexchange interaction of Co-S-Co bonds, consistent with the Goodenough–Kanamori rules. Notably, CoAl2S4 displays robust ferromagnetism with a Curie temperature reaching up to 435 K. The band structures show a large half-metal gap (2.83eV), ensuring the stability of the half-metallic state. Additionally, the CoAl2S4 monolayer demonstrates a preferential easy magnetization along the out-of-plane direction. Consequently, the rich CoAl2S4 monolayer is expected to boost advancements in spintronics, magnetostrictive materials, and magnetic memory devices.

Intrinsic room-temperature ferromagnetism in two-dimensional ternary transition metal tellurides CrX2Te4 (X = Al, Ga, and In)

A tremendous amount of research has witnessed the exploration of two-dimensional (2D) materials with intrinsic ferromagnetism and diverse physical properties. However, the low Curie temperature and deficient magnetic anisotropy hinder their practical applications in nanoscale spintronics. Based on first-principles calculations, we propose a new family of 2D ternary transition metal tellurides, CrX2Te4 (X = Al, Ga, and In), with both structural and magnetic stabilities at room temperature. Our calculations demonstrate that the 2D CrX2Te4 crystal exhibits the intrinsic 100% spin-polarized half-metallic feature with spin-up metallic and spin-down semi-conducting properties. With the remarkable magnetic moment of 4 μB per Cr atom, both 2D CrAl2Te4 and CrGa2Te4 crystals perform robust ferromagnetism with the out-of-plane magnetic anisotropy, while the 2D CrIn2Te4 crystal prefers the in-plane easy magnetization axis. The Monte Carlo simulation based on the 2D Heisenberg model shows that the critical Curie temperatures of the 2D CrAl2Te4, CrGa2Te4, and CrIn2Te4 crystals could reach 466, 431, and 536 K, respectively. Moreover, the magnetic exchange strength and magnetic anisotropy could be further enhanced by the in-plane biaxial strain. The novel electronic and magnetic features promote 2D CrX2Te4 (X = Al, Ga, and In) crystals as a new family of two-dimensional intrinsic ferromagnetic materials for next-generation advanced spintronics.

Two-dimensional 1T′ α -VXY (X = S, Se, Te; Y = Cl, Br, I): A multifunctional vanadium chalcohalide family with room-temperature ferromagnetism and sliding ferroelectricity

Two-dimensional (2D) ferromagnetic materials with Curie temperature (Tc) above room temperature have great potential ranging from spintronics to information processing and storage. Here, we computationally design a series of 1T′α-VXY (X = S, Se, Te; Y = Cl, Br, I) monolayers with the X and Y atoms arranged alternately in the 2D plane. VXY monolayers are ferromagnetic semiconductors with Tc much higher than room temperature. Furthermore, the symmetry breaking of VXY bilayers leads to sliding ferroelectricity with large reversible out-of-plane electric polarization and moderate interlayer sliding barriers. We further show that half-metal-to-semiconductor nonvolatile field-effect switching can be achieved in multiferroic van der Waals heterostructures composed of VXY and In2S3 ferroelectric substrates due to the synergistic effect between the polarization field-induced band edge shifting and the selective charge transfer at the interface. These findings reveal a promising role of 2D Janus 1T′α-VXY in spintronics, ferroelectric, and multiferroic device applications.

Electronic structure and magnetothermal properties of two-dimensional ScCl.

Two-dimensional ferromagnetic materials with intrinsic half-metallic properties have strong application advantages in nanoscale spintronics. Herein, density functional theory calculations show that monolayer ScCl is a ferromagnetic metallic material when undoped (n = 0), and the transition from metal to half-metal occurs with the continuous doping of holes. On the contrary, as the concentration of doped electrons increases, the system will exhibit metallic characteristics, which is particularly evident from a variation in spin polarizability. Furthermore, we have discussed how doped carriers affect the shape of the Fermi surface and the Fermi velocity of electrons. Most importantly, Monte Carlo simulations show that the ScCl monolayer is particularly regulated by carrier concentration (n) and magnetic field (h). Additionally, trends in energy and magnetic exchange coupling in different magnetic configurations (AFM phase and FM phase) with different doping concentrations are presented. When n < -0.16, the material is not only a half-metallic material that easily flips the magnetic axis, but also proves to be a candidate ferromagnetic material that works stably at room temperature in terms of dynamic stability. In addition, the origin of magnetocrystalline anisotropy is analyzed, and the contribution of different orbitals to spin-orbit coupling is presented. Moreover, we note that when magnetic field is small (h < 1 T), the change in size has a significant effect on ferromagnetic phase transition. However, when the system size is large (size >15 nm), TC is less sensitive to magnetic field. In addition, hole doping and size effect will greatly affect the hC of the system, but when the hole doping exceeds the critical value (n = -0.16), its influence on the hysteresis loop is no longer obvious. These interesting magnetic phenomena and easily adjustable physical properties show us that monolayer ScCl will be a promising functional material.

Air stability and composition evolution in van der Waals Fe3GeTe2

Layered two-dimensional ferromagnetic materials have emerged as a promising platform for spintronic applications, owing to their extraordinary physical properties. Remarkably, the representative two-dimensional ferromagnet Fe3GeTe2 has been extensively investigated due to its high Curie temperature and strong perpendicular magnetic anisotropy, which are beneficial for high-density storage at room temperature. However, there are few reports on its stability in the air and the surface oxidation products, which may prohibit its future application. Here, we report the natural oxidation process of Fe3GeTe2 films grown by molecular beam epitaxy evolved in the atmosphere, which was studied by x-ray photoelectron spectroscopy measurements and transmission electron microscopy. Our research shows that the surface of the Fe3GeTe2 film is oxidized quickly when exposed to air and shows two obviously evolving stages in the whole oxidation process. In the first stage, metallic Ge atoms are almost completely oxidized to form Ge–O bonds in GeO2, while partial metallic Fe and Te atoms are oxidized into Fe2O3 and TeO2, respectively. The second stage of oxidation is dominated by changes in the valence state of the Fe element, where Fe2O3 is reduced to FeCO3 through the participation of carbon adsorbed on the surface with the final oxidation product of FeCO3 · GeO2 · TeO2. Our findings provide insight into the subsequent growth and protection of Fe3GeTe2 thin films, which is of great significance for in-depth study and further application of spintronic devices in two-dimensional limits.

Two-dimensional monolayer CrGaS3: A ferromagnetic semiconductor with high Curie temperature and tunable magnetic anisotropy

Two-dimensional (2D) intrinsic ferromagnetic (FM) materials are promising candidates for fabricating next generation high-performance spintronic devices. However, all experimentally verified 2D FM semiconductors have Curie temperature (Tc) far below room temperature, which hinders their practical applications. Based on first-principles calculations, a stable and previously undiscovered 2D CrGaS3 structure is predicted, which is a semiconductor with an indirect bandgap of 1.99 eV and displays out-of-plane magnetic anisotropy. More importantly, it exhibits high-temperature ferromagnetism, with Tc ranging between 520 and 814 K. The high Tc is attributed to the presence of both direct-exchange and super-exchange interactions that are ferromagnetic, along with the eg-px/py-eg super exchange having a zero virtual exchange gap. Furthermore, it has been observed that the magnetic anisotropy can be tuned by external strain. These findings indicate its potential as a promising candidate for the rapid development of 2D spintronic applications.

Near room-temperature ferromagnetism in BixCr1−xTe2 epitaxial thin films grown on GaAs(111)B by molecular beam epitaxy

Two-dimensional (2D) ferromagnetic materials (FMs) are potentially the material foundation for future spintronics devices. However, at present, the Curie temperature (TC) of most 2D FM is relatively low and cannot meet the need for practical applications. Nowadays, CrTe2 thin films grown by molecular beam epitaxy (MBE) are reported to be room-temperature ferromagnetic only on graphene substrate instead of 3D substrates. In this work, we report high-quality Bi-doped CrTe2 (BixCr1−xTe2) thin films grown on conventional substrates of GaAs(111)B by MBE. Magnetotransport measurements reveal strong ferromagnetism of all the films, with out-of-plane magnetic anisotropy. More importantly, as more Bi atoms are doped into the film, the Curie temperature increases and reaches 305 K at x = 0.1. This improvement is a step forward for its application in spintronics and other fields.

Two-dimensional HfCr2N4 semiconductor with intrinsic room-temperature ferromagnetism and enhanced conductivity via electrostatic doping

Two-dimensional semiconductors with room-temperature intrinsic ferromagnetism and superior conductivity are crucial components for low-dimensional semiconductor spintronic devices. Based on density functional theory and Boltzmann transport theory, we investigate the electromagnetic and transport properties of the HfCr2N4 monolayer and modulate these properties via electrostatic doping. The HfCr2N4 monolayer is an intrinsic ferromagnetic semiconductor with a narrow band gap of 0.18 eV. The notably high Curie temperature of 719 K is highly desired for the practical applications of two-dimensional ferromagnetic materials. Under electrostatic doping, the HfCr2N4 monolayer maintains its ferromagnetic ground state, easy magnetization xy-plane, and high Curie temperature. Interestingly, owing to the narrow band gap of the HfCr2N4 monolayer, a significant enhancement in conductivity is observed at lower carrier doping concentrations, leading to a transition from a semiconductor to a half-metal. These unique features can be utilized to represent binary states ‘0’ and ‘1’. Our results indicate that the HfCr2N4 monolayer emerges as an ideal candidate for dual-gate field effect transistors.

CrO&lt;sub&gt;2&lt;/sub&gt; monolayer: a two-dimensional ferromagnet with high Curie temperature and half-metallicity

Owing to the complete spin-polarization of electronic states near Fermi energy, half-metallic ferromagnets, especially two-dimensional half-metallic ferromagnets, have garnered significant attention in the field of spintronics. However, the practical applications of these materials are greatly hindered by their low Curie temperatures. Therefore, the exploration of high Curie temperature half-metallic ferromagnets poses a necessary and challenging task. In this study, we predict a two-dimensional transition metal oxide, CrO&lt;sub&gt;2&lt;/sub&gt; monolayer, and employ first-principles calculations to investigate the crystal structure, electronic properties, magnetic ground state, and ferromagnetic phase transition. The calculations of phonon spectrum, elastic constant, and molecular dynamics simulations indicate that CrO&lt;sub&gt;2&lt;/sub&gt; monolayer is dynamically, mechanically, and thermally stable. The convex hull diagram of Cr-O systems shows that the hull energy of the predicted CrO&lt;sub&gt;2&lt;/sub&gt; layer is only 0.18 eV, further confirming the structural stability and large possibility for experimental fabrication. More importantly, the electronic and magnetic properties of CrO&lt;sub&gt;2&lt;/sub&gt; monolayer demonstrate that it is a two-dimensional ferromagnetic half-metal with wide band gap. Five d suborbitals are divided into E&lt;sub&gt;g&lt;/sub&gt; and T&lt;sub&gt;2g&lt;/sub&gt; orbitals because of the crystal field of Cr atom in the center of O tetrahedron, and the spin-polarizations of E&lt;sub&gt;g&lt;/sub&gt; orbitals make a major contribution to the moment around Cr atom. The ferromagnetic coupling along Cr-O-Cr chain is dominated by the superexchange interaction bridged by O 2p orbitals, similar to the typical Mn-O-Mn superexchange model. The magnetic behavior of the Cr spin lattice in a CrO&lt;sub&gt;2&lt;/sub&gt; monolayer is described by a two-dimensional Heisenberg model, in which the exchange coupling anisotropy is ignored and the single ion anisotropy is the main consideration. By solving the Heisenberg model through using the Monte Carlo simulation method, the Curie temperature is determined to be over 400 K. The high Curie temperature ferromagnetism is rare in two-dimensional ferromagnetic materials and even rarer in semi-metallic materials, which makes it an ideal material for fabricating spintronic devices and studying spin quantum effects.

Recent advances in two-dimensional intrinsic ferromagnetic materials Fe3X(X=Ge and Ga)Te2 and their heterostructures for spintronics.

Owing to their atomic thicknesses, atomically flat surfaces, long-range spin textures and captivating physical properties, two-dimensional (2D) magnetic materials, along with their van der Waals heterostructures (vdWHs), have attracted much interest for the development of next-generation spin-based materials and devices. As an emergent family of intrinsic ferromagnetic materials, Fe3X(X=Ge and Ga)Te2 has become a rising star in the fields of condensed matter physics and materials science owing to their high Curie temperature and large perpendicular magnetic anisotropy. Herein, we aim to comprehensively summarize the recent progress on 2D Fe3X(X=Ge and Ga)Te2 and their vdWHs and provide a panorama of their physical properties and underlying mechanisms. First, an overview of Fe3X(X=Ge and Ga)Te2 is presented in terms of crystalline and electronic structures, distinctive physical properties and preparation methods. Subsequently, the engineering of electronic and spintronic properties of Fe3X(X=Ge and Ga)Te2 by diverse means, including strain, gate voltage, substrate and patterning, is surveyed. Then, the latest advances in spintronic devices based on 2D Fe3X(X=Ge and Ga)Te2 vdWHs are discussed and elucidated in detail, including vdWH devices that exploit the exchange bias effect, magnetoresistance effect, spin-orbit torque effect, magnetic proximity effect and Dzyaloshinskii-Moriya interaction. Finally, the future outlook is given in terms of efficient large-scale fabrication, intriguing physics and important technological applications of 2D Fe3X(X=Ge and Ga)Te2 and their vdWHs. Overall, this study provides an overview to support further studies of emergent 2D Fe3X(X=Ge and Ga)Te2 materials and related vdWH devices for basic science and practical applications.

Tunable long-range spin transport in a van der Waals Fe3GeTe2/WSe2/Fe3GeTe2 spin valve.

The seamless integration of two-dimensional (2D) ferromagnetic materials with similar or dissimilar materials can widen the scope of low-power spintronics. In this regard, a vertical van der Waals (vdW) heterostructure of 2D ferromagnets with semiconducting transition metal dichalcogenides (TMDCs) forms magnetic junctions with exceptional stability and electrical control. Interestingly, 2D metallic Fe3GeTe2 (FGT) reveals above room temperature Curie temperatures and has large magneto anisotropy due to spin-orbit coupling. In addition, it also possesses topological states and a large Berry curvature. Herein, we designed the FGT/WSe2/FGT vdW heterostructure with a uniform and sharp interface so that FGT could maintain its inherent electronic properties. Also, the uniform thickness of the barrier provides a smooth flow of spins through the junctions as tunneling exponentially decays with an increasing barrier thickness. However, strong energy-dependent spin polarization is crucial for achieving optimum spin valve properties, such as large tunneling magnetoresistance (TMR) along with the manipulation of the magnitude and sign reversal. We have observed a shifting of high-energy localized minority spin states toward low-energy regions, which causes spin polarization fluctuation between -42.5% and 41% over a wide range of bias voltage. This leads to a negative TMR% of ∼-100% at 0.1 V Å-1 and also a large positive TMR% at 0.2 V Å-1 and -0.4 V Å-1. Besides, the system exhibits a highly tunable large anomalous Hall conductivity (AHC) of 626 S cm-1. Interestingly, such unprecedented electronic behaviour with large and switchable spin polarization, anomalous Hall conductivity and TMR can be incorporated into MTJ devices, which provide electrical control and long-range spin transport. Additionally, the system emerges as a standout candidate in low-power spintronic devices (e.g., MRAM and magnetic sensors) owing to its distinctive energy-dependent electronic structure with a wide range of external bias.

Toward intrinsic ultra-high-temperature ferromagnetism in a CrAuTe2/graphene heterosystem.

Exploring intrinsic two-dimensional (2D) ferromagnetic (FM) materials with high Curie temperatures (TC) and large magnetic anisotropy energies (MAE) is one of the effective solutions to develop materials for high-performance spintronic applications. Using density functional theory calculations and high-throughput computations, we predict an intrinsic bimetallic FM monolayer, CrAuTe2, which has a large MAE and high TC. The results show that the value of the MAE can reach about 1.5 meV per Cr, and Monte Carlo simulations show that the TC of monolayer CrAuTe2 is about 840 K. Further analysis indicates that the joint effects of spin-orbit coupling (SOC) interaction and magnetic dipole-dipole interaction result in high in-plane magnetic anisotropy. In addition, this monolayer has good dynamic, thermal, and mechanical stabilities, which were confirmed by ab initio molecular dynamics simulations, phonon spectra, and elastic constants, respectively. In order to propose a practical synthesis approach, we built a CrAuTe2/graphene van der Waals heterostructure, and found that the heterostructure does not affect the magnetic properties of monolayer CrAuTe2. These findings appear promising for the future applications in nano-spintronics.

Above-Room-Temperature Ferromagnetism in Copper-Doped Two-Dimensional Chromium-Based Nanosheets.

Two-dimensional ferromagnetic materials (2D-FMs) are expected to become ideal candidates for low-power, high-density information storage in next-generation spintronics devices due to their atomically ultrathin and intriguing magnetic properties. However, 2D-FMs with room-temperature Curie temperatures (Tc) are still rarely reported, which greatly hinders their research progress and practical applications. Herein, ultrathin Cu-doped Cr7Te8 FMs were successfully prepared and can achieve above-room-temperature ferromagnetism with perpendicular magnetic anisotropy via a facile chemical vapor deposition (CVD) method, which can be controlled down to an atomic thin layer of ∼3.4 nm. STEM-EDX quantitative analysis shows that the proportion of Cu to metal atoms is ∼5%. Moreover, based on the anomalous Hall effect (AHE) measurements in a six-terminal Hall bar device without any encapsulation as well as an out-of-plane magnetic field, the maximum Tc achieved ∼315 K when the thickness of the sample is ∼28.8 nm; even the ultrathin 7.6 nm sample possessed a near-room-temperature Tc of ∼275 K. Meanwhile, theoretical calculations elucidated the mechanism of the ferromagnetic enhancement of Cu-doped Cr7Te8 nanosheets. More importantly, the ferromagnetism of CVD-synthesized Cu-doped CrSe nanosheets can also be maintained above room temperature. Our work broadens the scope on room-temperature ferromagnets and their heterojunctions, promoting fundamental research and practical applications in next-generation spintronics.

Intrinsic valley polarization and anomalous valley Hall effect in monolayer [formula omitted]-ScAt[formula omitted

Materials with spontaneous polarization is very promising in valley electronics because of its potential application in encoding and storing information. In this paper, we proposed a stable two-dimensional ferromagnetic valley material H-ScAt2 which can spontaneously generate valley splitting and exhibit intrinsic anomalous Hall effect. The valley polarization is 0.245 eV, which is large than most of the reported materials. The structural stability is verified by our phonon and molecular dynamic calculation. The Curie temperature of H-ScAt2 monolayer is about 840 K, which is above room temperature.

Electronic structure and magnetic properties of CrI3 monolayer doped by rare earth metal atoms

CrI3 monolayer is a two-dimensional (2D) ferromagnetic (FM) semiconductor materials with broad application prospects in the field of spintronics due to its magnetic semiconductor feature and unique 2D structure. In this work, we employ first-principles calculations based on density functional theory to investigate the electronic structure and magnetic properties of CrI3 monolayer doped with rare earth (RE) metal atoms (RE = Sc, Y, La, Ce, Pr, Nd, Pm, Eu, Gd, Tm, and Lu). The results demonstrate that doping with RE atoms enables the control of total magnetic moments and a significantly enhancement of the Curie temperature of CrI3 monolayer. Especially, the Curie temperature of CrGdI6 monolayer reaches 347.58 K, which could be a promising candidate for realizing room temperature ferromagnetism. Furthermore, by applying strain and electric field, the CrREI6 monolayers exhibit metal, half-metal and spin gapless semiconductor properties. These findings not only provide valuable insights into the manipulation of electronic structure and magnetic properties in CrI3 monolayer but also establish RE doped CrI3 monolayer as a promising material for spintronic devices.