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We investigate the individual and combined effects of substitutional Mn-doping and strain engineering in monolayers of MoS2 and MoSe2, using density functional theory (DFT) to examine the structural, electronic, and magnetic properties. Doping with Mn is shown to introduce magnetic character by producing localized spin polarization in the region near the defect. The Mn dopants preferentially couple ferromagnetically due to an interaction that is described as double exchange. Additionally, doping with Mn changes the electronic structure by introducing defect states within the band gap, which according to one form of DFT, results in half-metallic character. Compressive and tensile strain both decrease the band gap in the pure transition metal dichalcogenides (TMDs), retaining the materials' semiconducting character. Strain has a multi-varied effect on the electronic properties in the Mn-doped TMDs. Tensile strain demonstrates potential to strengthen ferromagnetic coupling, offering new possibilities for strain-engineering dilute magnetic semiconductors with more enhanced stability at room temperature. [ABSTRACT FROM AUTHOR]

In the current study, the structural, electronic and magnetic properties of Zn 1-x V x S (at x = 0.125 and 0.25) have been investigated using full-potential linearized augmented plane wave plus local orbital (FP-LAPW + lo) method within the density functional theory (DFT). The Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) has been applied for optimizing the structural properties. The electronic and magnetic properties were studied by both PBE-GGA and modified Becke and Johnson local spin density approximation (mBJ-LSDA). Results show that the Zn 1-x V x S (at x = 0.125 and 0.25) structures are more stable in the ferromagnetic phase. The density of states and band structure calculations reveal that these compounds exhibit half metallic character with 100% spin polarization at the Fermi level. The energy gap in the minority spin channel increases with an increase in concentration of doping. The values of p–d exchange splitting ΔE v and p–d exchange constants N 0 β are negative, which confirms that the effective potential is more attractive for the minority spin states. Also, it is found that exchange constants N 0 α and N 0 β decreases with the increasing concentration of vanadium, which confirms the ferromagnetic character of these compounds. The calculated total magnetic moments for Zn 1-x V x S are about 3 μB largely arisen from the vanadium doping. [ABSTRACT FROM AUTHOR]

We have investigated the half metallic ferromagnetism in (Mn,Cr) codoped ZnS using first principles calculations. While, Cr doped ZnS (ZnS:Cr) exhibits half-metallic ferromagnetic character, Mn doped ZnS (ZnS:Mn) is not found to be half-metallic. When Cr codoped to ZnS:Mn, it is found to transform into a half-metallic ferromagnetic semiconductor. The effect of occupation of Cr and Mn at two different sites of Zn atoms has brought out conspicuous difference in the band structure and density of states. The positional differences of Cr and Mn give rise to different characteristics, while in one case half-metallic nature is shown, in other case, there is no half-metallic nature. The half-metallic (Mn,Cr) codoped ZnS shows 100% spin polarization. Exchange constants clearly illustrates that all the compounds are in ferromagnetic order and the ferromagnetic coupling is mediated through the direct exchange interaction. [ABSTRACT FROM AUTHOR]

(In1−xDyx)2O3 (x = 0, 0.05, 0.10) nanoparticles with a particle size of 15–22 nm were obtained by an auto-combustion method. The powder x-ray diffraction (XRD), Raman and x-ray absorption near edge spectral (XANES) analysis revealed a cubic bixbyite structure (space group Ia-3). The presence of Dy3+ ions in the In2O3 host lattice was confirmed from XPS data. The high-resolution transition electron microscopic (HRTEM) and XANES revealed the single phase (solid solution) nature of the nanoparticles. The optical band gap was found to increase from 3.57 eV to 3.64 eV by doping Dy into the In2O3 lattice. Photoluminescence spectra shows emission in the yellow region probably due to oxygen related vacancies. A weak ferromagnetic property was seen for Dy-doped In2O3 at room temperature, while pure In2O3 is diamagnetic. It seems that Dy:In2O3 is not a suitable␣system to consider for dilute magnetic semiconductors in spintronic devices. [ABSTRACT FROM AUTHOR]

Dilute magnetic semiconductors (DMS), achieved through substitutional doping of spin‐polarized transition metals into semiconducting systems, enable experimental modulation of spin dynamics in ways that hold great promise for novel magneto–electric or magneto–optical devices, especially for two‐dimensional (2D) systems such as transition metal dichalcogenides that accentuate interactions and activate valley degrees of freedom. Practical applications of 2D magnetism will likely require room‐temperature operation, air stability, and (for magnetic semiconductors) the ability to achieve optimal doping levels without dopant aggregation. Here, room‐temperature ferromagnetic order obtained in semiconducting vanadium‐doped tungsten disulfide monolayers produced by a reliable single‐step film sulfidation method across an exceptionally wide range of vanadium concentrations, up to 12 at% with minimal dopant aggregation, is described. These monolayers develop p‐type transport as a function of vanadium incorporation and rapidly reach ambipolarity. Ferromagnetism peaks at an intermediate vanadium concentration of ~2 at% and decreases for higher concentrations, which is consistent with quenching due to orbital hybridization at closer vanadium–vanadium spacings, as supported by transmission electron microscopy, magnetometry, and first‐principles calculations. Room‐temperature 2D‐DMS provide a new component to expand the functional scope of van der Waals heterostructures and bring semiconducting magnetic 2D heterostructures into the realm of practical application. [ABSTRACT FROM AUTHOR]

The geometric structures, electronic and magnetic properties of Mn-doped ZnO nanowires were investigated using density functional theory. The results indicated that all the calculated energy differences were negative, and the energy of the ground state was 0.229 eV lower than ferromagnetic coupling, which show higher stability in antiferromagnetic coupling. The calculated results indicated that obvious spin splitting phenomenon occurred near the Femi level. The Zn atoms on the inner layer of ZnO nanowires are easily substituted by Mn atoms along the [0001] direction. It was also shown that the Mn2+-O2--Mn2+ magnetic coupling formed by intermediate O atom was proved to be caused by orbital hybridization between Mn 3d and O 2p states. The magnetic moments were mainly attributed to the unpaired Mn 3d orbitals, but not relevant with doping position of Mn atoms. Moreover, the optical properties of Mn-doped ZnO nanowires exhibited a novel blue-shifted optical absorption and enhanced ultraviolet-light emission. The above results show that the Mn-doped ZnO nanowires are a new type of magneto-optical materials with great promise. [ABSTRACT FROM AUTHOR]

The fine crystalline structure of metastable cubic oxide compounds NiZnO (0.6 ≤ x ≤ 0.99) has been examined using X-ray diffraction. The compounds have been synthesized from the original hexagonal phase by quenching specimens from an elevated temperature under an external hydrostatic pressure. It has been found that the diffraction patterns of the compounds include a system of superlattice diffuse maxima, the number and intensity of which depend greatly on their composition. The origin of this superstructure is discussed. [ABSTRACT FROM AUTHOR]

Dilute magnetic semiconductors (DMS) are envisioned as sources of spin-polarized carriers for future semiconductor devices which simultaneously utilize spin and charge of the carriers. The hope of discovering a DMS with ferromagnetic order up to room temperature still motivates research on suitable DMS materials. Two candidate wide-band gap DMS are Gd:GaN and Co:ZnO. We have used hard X-ray absorption spectroscopy (XAS) and in particular X-ray linear dichroism (XLD) and X-ray magnetic circular dichroism (XMCD) to study both DMS materials with element specificity and compare these findings with results from integral SQUID magnetometry as well as electron paramagnetic resonance (EPR). [ABSTRACT FROM AUTHOR]

Wide-bandgap dilute magnetic semiconductors (DMS), such as transition-metal doped ZnO and GaN, have gained attention for use in spintronic devices because of predictions and experimental reports of room temperature ferromagnetism which may enable their use in spintronic devices. However, there has been some debate over the source of ferromagnetism in these materials. This paper focuses on the high quality growth of wide bandgap DMS, and the characterization of Zn1-xMnxO produced by melt-growth techniques and Ga1-xMnxN grown by metal organic chemical vapor deposition (MOCVD). High resolution X-ray diffraction results revealed no second phases in either the ZnO crystals or the GaN films. Undoped as-grown, bulk crystals of Zn1-xMnxO and Zn1-xCoxO crystals are shown to be paramagnetic at all temperatures. In contrast, the Ga1-xMnxN films showed ferromagnetic behavior at room temperature under optimum growth conditions. Experimental identification of the Mn ion charge state and the presence of bands in the bandgap of GaN are investigated by optical spectroscopy and electron spin paramagnetic resonance (EPR). It is shown that the broadening of states in the Mn 3d shell scaled with Mn concentration, and that optical transitions due to this band correlated with the strong ferromagnetism in these samples. However, this band disappeared with an increase in free electron concentration provided by either annealing or doping. Raman studies of Ga1-xMnxN revealed two predominant Mn-related modes featured with increasing concentration, a broad disorder related structure at 300cm-1 and a sharper peak at 669cm-1 This works show that the development of practical ferromagnetic wide bandgap DMS materials for spintronic applications will require both the lattice site introduction of Mn as well as careful control of the background defect concentration to optimize these materials. [ABSTRACT FROM AUTHOR]