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The all-surface nature of atomically thin van der Waals materials can present challenges for practical applications. Fortunately, new layered materials are on the horizon that preserve their useful properties even when thicker than a monolayer. Here, we summarize our interest in one of these emergent materials, the magnetic semiconductor CrSBr. We describe monolayer properties exhibited by this material in its bulk form, discussing how the quasi-1D electronic structure of CrSBr allows mono- or bilayer physics to be displayed even in thick crystals. Long-range magnetic order offers additional tuning with the coupled lattice, spin, orbit, and charge degrees of freedom enabling magneto-correlated phenomena. We discuss the stability of CrSBr in air and show atomic scale structural manipulation through electron beam-driven transformations. We conclude that the stability and structural amenability of CrSBr provide opportunities for imagining devices that use bulk crystals yet exploit unique magnetic and quantum confinement effects. Graphical abstract

We present first-principles density-functional calculations for the structural, electronic, and magnetic properties of substitutional 3 d transition metal (TM) impurities in two-dimensional black and blue phosphorenes. We find that the magnetic properties of such substitutional impurities can be understood in terms of a simple model based on the Hund’s rule. The TM-doped black phosphorenes with Ti, V, Cr, Mn, Fe, and Ni impurities show dilute magnetic semiconductor (DMS) properties while those with Sc and Co impurities show nonmagnetic properties. On the other hand, the TM-doped blue phosphorenes with V, Cr, Mn, and Fe impurities show DMS properties, with Ni impurity showing half-metal properties, whereas Sc- and Co-doped systems show nonmagnetic properties. We identify two different regimes depending on the occupation of the hybridized electronic states of TM and phosphorous atoms: (i) bonding states are completely empty or filled for Sc- and Co-doped black and blue phosphorenes, leading to nonmagnetic; (ii) non-bonding d states are partially occupied for Ti-, V-, Cr-, Mn-, Fe- and Ni-doped black and blue phosphorenes, giving rise to large and localized spin moments. These results provide a new route for the potential applications of dilute magnetic semiconductor and half-metal in spintronic devices by employing black and blue phosphorenes. PACS numbers: 73.22.-f, 75.50.Pp, 75.75. + a

We perform systematic first-principles calculations on the electronic structure of n-type magnetic semiconductor Ba(Zn1−xCox)2As2 with the facilitation of HSE06 hybrid functional. Supercells are used to consider the doping of Co atoms, and the first-principles band structures are unfolded for clarity. Based on the calculation results, magnetic states are preferred by individual Co atoms doped in Ba(Zn1−xCox)2As2 at diluted limit, and carriers are originated mainly from situations where only one Co atom exists in the nearest neighbor Zn sites out of certain doped Co atoms. The origination of carriers can be explained by the density of states and the unfolded band structure, where it is found that the scattering effects from single Co atom is small but quite large when more Co atoms are located at adjacent Zn sites. The large scattering effects of two adjacent Co atoms will alter the band structures near the Fermi-level. Carriers in Ba(Zn1−xCox)2As2 mainly originate from the As-4p orbitals, with partial contributions from the Co-3d orbitals. Our work provides new insights into the origin of the n-type carriers in magnetic semiconductors and will inspire the development of new magnetic semiconducting systems.

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 AlNTiO 2 , ZnO, SnO 2 , 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.

In this work, the magnetic and thermodynamic properties of dilute magnetic semiconductor quantum dots of cylindrical geometry are investigated. The eigenvalue of the quantum system we are considering is obtained by solving the one-electron Schrödinger equation within the framework of the effective mass approach. Then, taking into account the energy spectrum, expressions for thermodynamic quantities and magnetic susceptibility are obtained. The behavior of these expressions depending on temperature is studied using the parameters B , x , R 0 and L 0 . Based on the results obtained, it is established that the average energy, free energy, heat capacity, entropy and magnetic susceptibility at low temperatures depend on the parameter x . Also at low temperatures, when x = 0 , the average energy and free energy exhibit a linear relationship. With increasing temperature, this dependence becomes nonlinear. For x ≠ 0 , the dependence of the average energy and free energy on temperature is a rapidly increasing nonlinear function. In addition, when x ≠ 0 , magnetic susceptibility reaches a maximum at low temperatures. The peak height increases with x and disappears when x = 0 . The peak of magnetic susceptibility decreases as the magnetic field increases when x ≠ 0 and shifts toward higher temperatures. The specific heat forms a Schottky peak at low temperatures and asymptotically approaches C v = 3 k B at high temperatures.

Cluster-assembled materials have attracted particular attention for their complex hierarchical structures and unique properties. However, the majority of cluster-based assemblies developed so far are either non-magnetic or only exhibit magnetic ordering with a relatively low Curie temperature, limiting their applications in spintronics. Thus, two-dimensional (2D) cluster-assembled materials with room-temperature magnetism remain highly desirable. For this purpose, based on first principles calculations, we design a series of thermodynamically stable 2D cluster-based metal-organic frameworks (MOFs) Fe n -(pyz) ( n =1–6) by utilizing Fe n metal clusters as nodes and nitrogen-containing pyrazine ligands as organic linkers. These 2D cluster-based MOFs exhibit robust ferrimagnetic ordering due to the strong d–p direct exchange interaction between d-electron spin of Fe n ( n =1–6) clusters and charge transfer-induced p -electron spin of pyrazine ligands. In particular, the ferrimagnetic Curie temperatures are well above room temperature (up to 836 K). Additionally, altering the size of Fe n clusters in Fe n -(pyz) ( n =1–6) MOFs results in diverse functional spintronic properties, including bipolar magnetic semiconductors, half semiconductors and Dirac half metals. Moreover, these 2D assembled MOFs possess sizable magnetic anisotropy energies, up to 9.16 meV per formula.

Exploring two-dimensional (2D) magnetic semiconductors with room-temperature magnetic ordering and electrically controllable spin-polarization is a highly desirable but challenging task for nano-spintronics. Here, through first-principles calculations, we propose to realize such a material by exfoliating the recently synthesized organometallic layered crystal Li 0.7 [Cr(pyz) 2 ]Cl 0.7 ·0.25(THF) (pyz=pyrazine, THF=tetrahydrofuran). The feasibility of exfoliation is confirmed by the rather low exfoliation energy of 0.27 J m −2 , even smaller than that of graphite. In exfoliated Cr(pyz) 2 monolayers, each pyrazine ring grabs one electron from the Cr atom to become a radical anion, and then a strong d-p direct-exchange magnetic interaction emerges between Cr cations and pyrazine radicals, resulting in room-temperature ferrimagnetism with a Curie temperature of 342 K. Moreover, the Cr(pyz) 2 monolayer is revealed to be an intrinsic bipolar magnetic semiconductor where electrical doping can induce half-metallic conduction with controllable spin-polarization direction.

A ferromagnetic coupling between localized Mn spins was predicted in a series of ab initio and tight binding calculations and experimentally verified for the dilute magnetic semiconductor Ga1−xMnxN. In the limit of small Mn concentrations, x ≲ 0.01, the paramagnetic properties of this material were successfully described using a single ion crystal field model approach. In order to obtain the description of magnetization in (Ga,Mn)N in the presence of interacting magnetic centers, we extend the previous model of a single substitutional Mn3+ ion in GaN by considering pairs, triplets and quartets of Mn3+ ions coupled by a ferromagnetic superexchange interaction. Using this approach we investigate how the magnetic properties, particularly the magnitude of the uniaxial anisotropy field, change as the number of magnetic Mn3+ ions in a given cluster increases from 1 to 4. Our simulations are then exploited in explaining experimental magnetic properties of Ga1−xMnxN with x ≅ 0.03, where the presence of small magnetic clusters gains in significance. As a result the approximate lower and upper limits for the values of exchange couplings between Mn3+ ions in GaN, being in nearest neighbors (nns) Jnn and next nns Jnnn positions, respectively, are established.

Dilute magnetic semiconductor nanoparticles of zinc phosphide (Zn 3-x Ni x P 2 ), doped with nickel, were synthesized using a solid-state reaction method. The doping levels of nickel were varied at x  = 0.01, 0.03, 0.05, and 0.07. The study investigated the influence of varying nickel dopant concentrations on the structural, optical, and magnetic characteristics of the synthesized materials. Based on the XRD investigation, it is evident that the generated samples have a tetragonal structure, with no discernible presence of additional nickel or any other contaminants in the diffraction peaks. The lattice parameters exhibited a positive correlation with the Ni content, indicating that an increase in Ni concentration led to an increase in lattice parameters. SEM pictures provided empirical evidence supporting the notion that the dimensions of the nanoparticles exhibited a positive correlation with the extent of dopant incorporation. EDS examination indicates that the concentration of dopants closely approximates the desired atomic ratio. The optical band gap of the Zn 3-x Ni x P 2 nanoparticles exhibited a rise in value, namely from 1.410 to 1.433 eV, as the quantity of nickel was increased. The study revealed that photoluminescence emission peaks were consistently seen at nearly identical places, despite variations in excitation wavelengths. Additionally, it was noted that the strength of the emission peaks exhibited slight fluctuations, which were more pronounced as the concentration of the dopant rose. The study of the VSM data demonstrates a positive correlation between saturation magnetization and the Ni content, indicating that an increase in the Ni concentration leads to an increase in saturation magnetization.

The magnetic excitons in diluted magnetic semiconductor (DMS) have varied formats due to the inhomogeneous phases out of doping concentration and/or structural relaxations or defects. Here the high quality cobalt-doped zinc blende ZnSe nanoribbons (NRs) were synthesized, showing bright and color-variable emissions from blue, yellow to a little mixed white colors. Their power and temperature dependent micro-photoluminescence (PL) spectra have been obtained in which two emission bands, one magnetic exciton band near the band-edge and a Co 2+ high-level d – d transition emission band at 550 nm out of their ferromagnetic (FM) coupled aggregates in ZnSe lattice, both bands could also be reflected by a nonlinear optical absorption enhancement. The easy formed stacking fault defects in a chemical vapor deposition (CVD) grown ZnSe zincblende NR took part in the above optical processes out of magnetic polaronic excitons (PXs). The femtosecond (fs) laser pulse pumping on single ZnSe:Co NR produces obvious lasing behavior but with profile of a complicated magnetic exciton interactions with indication of a crossover from collective exciton magnetic polarons (EMP) to bound magnetic polaron (BMP) scattering in Co doped ZnSe NR. These findings indicate the complication of the magnetic coupling natures in varied DMS structures, whose optical properties have been found to be highly nonlinear, due to the involvement of the spin–spin, spin–exciton and spin–phonon interactions, verified by the theoretic calculation in Yang X-T et al (2019 Interstitial Zn-modulated ferromagnetism in Co-doped ZnSe Mater. Res. Express 6 106121).