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Two-dimensional magnetic semiconductors provide a platform for studying physical phenomena at atomically thin limit, and promise magneto-optoelectronic devices application. Here, we report light helicity detectors based on graphene-CrI3-graphene vdW heterostructures. We investigate the circularly polarized light excited current and reflective magnetic circular dichroism (RMCD) under various magnetic fields in both monolayer and multilayer CrI3 devices. The devices exhibit clear helicity-selective photoresponse behavior determined by the magnetic state of CrI3. We also find abnormal negative photocurrents at higher bias in both monolayer and multilayer CrI3. A possible explanation is proposed for this phenomenon. Our work reveals the interplay between magnetic and optoelectronic properties in CrI3 and paves the way to developing spin-optoelectronic devices.

Sol–gel method was used to successfully produce dilute magnetic semiconductor ( $${\mathrm{Zn}}_{1-\mathrm{x}-\mathrm{y}}{\mathrm{Mn}}_{\mathrm{x}}{\mathrm{Cr}}_{\mathrm{y}}$$ O) nanoparticles. Fourier transforms infrared spectroscopy (FTIR) and electrical conductivity tests were used to investigate the structural and electrical properties of the prepared samples. FTIR spectra are used to examine the functional chemical bonding properties of various elements and compounds found in materials. The dopant's incorporation into the ZnO framework structure is confirmed by FTIR spectra. The dominance of the Mn–O or Cr–O interaction in the Zn–O–Mn or Zn–O–Cr bonds may result from an increase in Mn or Cr concentration in the wurtzite structure, which could lead to structural stress and defects. Within the frequency range of 0.042 kHz–1 MHz and the temperature range of 298–573(K), the conductivity (σac) was measured. The increase in conductivity values is more pronounced for samples with lower doping concentrations of Mn and Cr. The maximum $${\upsigma }_{\mathrm{ac}}$$ value is reached in the sample with 1.5% Mn and 0.5% Cr. The maximum ɛʹ value reached in the sample with 10% Cr. The prepared samples are considered as candidates for semiconductor materials in electronic devices.

Crystal structures, electronic, and magnetic properties of RbCeX2 (X = S, Se, Te) crystals are investigated using periodic density functional theory (DFT) calculations under hydrostatic pressures up to 10 GPa. The ferromagnetic phase is slightly more stable than the anti-ferromagnetic one for all compounds and pressures. A pressure-induced transition from a magnetic semiconductor (MS) to a spin gapless semiconductor (SGS) is observed only in the case of the X = Te compound. In absence of imposed pressure, the X = Te exhibits a direct α-spin gap of 0.46 eV while its β-gap is 2.30 eV. A pressure of 10 GPa completely suppresses the α-spin gap of RbCeTe2 and reduces it β-gap to 1.63 eV. This pressure-induced elimination of only one spin gaps is exclusive to the X = Te compound. This property distinguishes the Te compound from its two congeners. The pressure-response characteristics of RbCeTe2 renders this compound a potential pressure-induced MS → SGS switching material.

Doping of foreign atoms may substantially alter the properties of the host materials, in particular low-dimension materials, leading to many potential functional applications. Here, we perform density functional theory calculations of two-dimensional InSe materials with substitutional doping of lanthanide atoms (Ce, Nd, Eu, Tm) and investigate systematically their structural, magnetic, electronic and optical properties. The calculated formation energy shows that the substitutional doping of these lanthanide atoms is feasible in the InSe monolayer, and such doping is more favorable under Se-rich than In-rich conditions. As for the structure, doping of lanthanide atoms induces visible outward movement of the lanthanide atom and its surrounding Se atoms. The calculated total magnetic moments are 0.973, 2.948, 7.528 and 1.945 μB for the Ce-, Nd-, Eu-, and Tm-doped systems, respectively, which are mainly derived from lanthanide atoms. Further band structure calculations reveal that the Ce-doped InSe monolayer has n-type conductivity, while the Nd-doped InSe monolayer has p-type conductivity. The Eu- and Tm-doped systems are found to be diluted magnetic semiconductors. The calculated optical response of absorption in the four doping cases shows redshift to lower energy within the infrared range compared with the host InSe monolayer. These findings suggest that doping of lanthanide atoms may open up a new way of manipulating functionalities of InSe materials for low-dimension optoelectronics and spintronics applications.

Dilute magnetic semiconductors (DMSs), such as (In, Mn)As and (Ga, Mn)As prototypes, are limited to III–V semiconductors with Curie temperatures ( T c ) far from room temperature, thereby hindering their wide application. Here, one kind of DMS based on perovskite niobates is reported. BaM x Nb (1− x ) O 3− δ ( M = Fe, Co) powders are prepared by the composite-hydroxide-mediated method. The addition of M elements endows BaM x Nb (1− x ) O 3− δ with local ferromagnetism. The tetragonal BaCo x Nb (1− x ) O 3− δ nanocrystals can be obtained by Co doping, which shows strong saturation magnetization ( M sat ) of 2.22 emu g −1 , a remnant magnetization ( M r ) of 0.084 emu g −1 and a small coercive field ( H c ) of 167.02 Oe at room temperature. The ab initio calculations indicate that Co doping could lead to a 64% local spin polarization at the Fermi level ( E F ) with net spin DOS of 0.89 electrons eV −1 , this result shows the possibility of maintaining strong ferromagnetism at room temperature. In addition, the trade-off effect between the defect band absorption and ferromagnetic properties of BaM x Nb (1− x ) O 3− δ is verified experimentally and theoretically.

We present a computational model to model the magnetic structure of two-dimensional (2D) dilute-magnetic-semiconductors (DMS) both the monolayers and multilayers using first-principles density functional theory (DFT), as well as their magnetic phase transition as a function of temperature using Monte-Carlo simulations. Using our method, we model the magnetic structure of bulk, bilayer, and monolayer MoS2 substitutionally doped with Fe atoms. We find that the out-of-plane interaction in bilayer MoS2 is weakly ferromagnetic, whereas in bulk MoS2 it is strongly anti-ferromagnetic. Finally, we show that the magnetic order is more robust in bilayer Fe-doped MoS2 compared to the monolayer and results in a room-temperature FM at an atomic substitution of 14-16%.

We present density functional theory-based first principles study of magnetic properties of Mn-doped Mg[Formula: see text]Mn2On clusters. Mn-doped MgnOn clusters are found to exhibit antiferromagnetic order. We show that ferromagnetic state can be stabilized by codoping with carbon at oxygen site. Our study suggests that the holes created due to C doping are responsible for the stabilization of ferromagnetism.

To gain insight into the spin-glass state of diluted magnetic semiconductors, we have examined the magnetic and electronic properties of ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Te}$ using density-functional theory as well as performed magnetization measurements on the $x=0.43$ and 0.55 systems to demonstrate a clear spin-glass transition consistent with previous literature. Using a generalized gradient approximation, we investigate the electronic and magnetic properties for $x=0$, 0.075, 0.15, 0.25, and 0.50 doping levels using the magnetic moment of ${\mathrm{Mn}}^{2+}$ as guide for the dependence of the Hubbard onsite potential on the electronic structure. Simulations on both ferromagnetic (FM) and antiferromagnetic (AFM) configurations yield a distinct AFM ground-state preference, which is consistent with a zero-magnetic-moment spin-glass state. Here an onsite potential of up to 8 eV on the Mn $3d$ orbitals is needed to harden the magnetic moment toward $S=5/2$. From our analysis of the electronic structure evolution with doping and onsite potential, we confirm the semiconducting state of the Mn-doped ZnTe as well as show that the presence of Mn incorporated into the ZnTe matrix at the Zn lattice site produces magnetic interactions through the Te ions with a distinct Te-Mn $pd$-orbital hybridization. Furthermore, we show that this hybridization is activated with the Mn doping above 0.25 concentration, which corresponds to the doping level in which the spin-glass transition begins to rise. Therefore, it is likely that the coupling of $pd$-orbital hybridization of the Mn and Te $p$ orbitals is a precursor to the enhancement of the spin-glass transition temperature.

This theoretical work presents the electronic and magnetic properties of Cr doped SrFe12O19 using first-principles calculations based on density functional theory. An improvement in the magnetic properties of SrFe12O19 is predicted when doped with the Cr3+ ion. It was found that the magnetic Cr3+ ion preferentially replaces Fe3+ ion at 2a, 4f1, and 12k sites. The calculation demonstrates that if Cr ion occupies the 4f1 site, a total magnetization of 52.920 emu/g is obtained. On the other hand, SrFe11.5Cr0.5O19 behaves as a semiconductor when Cr occupies the 2a and 12k sites while behaves like half-metal when Cr occupies the 4f1 site. The higher magnetization, identified for the SrFe11.5Cr0.5O19 compound, provides unique qualities in the applications of permanent magnets and/or related devices like spintronics and magnetic semiconductors.

The structure and chemical composition of grain boundaries in GaSb magnetic semiconductors have been investigated. We determined that quenching of the GaSb melt with 2% Mn results in the formation of a textured polycrystal (111). The grain boundaries of the texture are formed by split 60 degree dislocations with dislocation lines. Microinclusions based on the ferromagnetic compound MnSb are located on the stacking faults of split dislocations. The chemical compositions of microinclusions differ, but their average composition is close to Mn1.1Sb. The synthesized GaSb is a soft ferromagnet with a coercive force of 10 Oe and a magnetic state approaching superparamagnetic

An analysis of ab initio numerical results obtained for the total energy of diluted magnetic semiconductors (DMSs) doped with dopant formations of various structural and spin conformations consisting of 2–4 3D transition metal (TM atoms) has revealed that a dopant formation acts as large impurity atom i.e., as a megatom, in a reverse analogy to the process of the adsorption of sp-atoms onto metallic surfaces. As a result, the d-orbitals of the magnetic dopant formation (the megatom) become hybridized with the sp-bands of the host anions thus creating a number of impurity states which are reflected in the changes of the band gap of the DMS establishing an implicit relationship between the band gap and magnetism. Additional findings also indicate that: (i) the total magnetic moment M tot ( α ) and the band gap e gap ( α ) which characterize a DMS with a dopant formation in spin conformation (α) do not vary independently from each other but instead form one composite system parameter. (ii) The per dopant-pair magnetic interactions in dopant formations consisting of more than two dopants are smaller than those obtained for an isolated dopant-pair. These are demonstrated with results obtained for GaN doped with 3D-TM dopant formations.

We consider a transverse electrical and spin current response to a longitudinal electric field in a metallic or semiconductor system characterized by various types of chirality. Using the similar theoretical approach we study a skew scattering on magnetic skyrmions leading to topological Hall effect, tunneling anomalous Hall effect (TAHE) of electrons and holes across an interface between magnetic semiconductors and electron scattering on a magnetic center in a semiconductor. We demonstrate how the chiral symmetry of the system manifests itself in the Hall response and its dependence on the electron spin polarization.

Functional materials combining the optoelectronic functionalities of semiconductors with control of the spin degree of freedom are highly sought after for the advancement of quantum technology devices and provide exciting avenues for polarized light-emission. Previous work towards this goal introduced small amounts of magnetic elements into crystalline semiconductor, e.g. through vacuum-based deposition, to obtain dilute magnetic semiconductors (DMS). In my talk, I will present our efforts on gaining control over spin dynamics and spin interactions through compositional and structural tuning in solution-processable hybrid perovskite semiconductors. We aim to exploit the exceptional optoelectronic properties of these hybrid perovskites, together with their tolerance in the electronic states to dopants and defects, to make advances towards high-performance DMS.

Documento de texto científico con imágenes a color relacionadas con los diferentes equipos de medición, teoría estudiada y fenomenología encontrada en las caracterizaciones de diferentes propiedades físicas. ilustraciones, gráficas, tablas Las estructuras cristalinas de las nuevas perovskitas complejas que componen la familia RAMOx (R = La, Nd, Sm, Eu; A = Sr, Bi; M = Ti, Mn, Fe), difirieren en sus propiedades debido a que los elementos que las conforman, al ser acoplados, crean enlaces que a pesar de cristalizar en el mismo grupo espacial Pnma o Pbnm (# 62) presentan ligeros cambios originados por las características magnéticas, eléctricas, de radio iónico y por el enlace iónico o covalente de los diferentes elementos químicos que las componen. Además, se observan pequeñas diferencias en las posiciones atómicas y parámetros reticulares en la estructura con fase mayoritaria encontrada (98% de pureza), lo que conduce a la vez a diferencias dadas por distorsiones o inclinación de sus octaedros B-O6, que al haber sido expuestas a diferentes mecanismos mecánicos, eléctricos, magnéticos o térmicos, dan origen a propiedades características de cada una de las siete fórmulas estequiométricas sintetizadas y posteriormente analizadas en este documento. Las muestras policristalinas se produjeron por medio del método de síntesis de reacción de estado sólido. Durante los diferentes procesos térmicos aplicados se obtuvo la evolución cristalina con desaparición de las reflexiones propias de los óxidos precursores a partir de los cuales fueron sintetizadas las muestras hasta la obtención de la fase cristalográfica final. El refinamiento Rietveld, mediante el uso del software GSAS, permitió obtener la estructura en que cristalizó cada compuesto y sus parámetros tanto cristalográficos como de confianza. El estudio microestructural, a través de imágenes que se obtuvieron por medio del SEM, mostró un buen grado de compactación de los granos, resultado cotejado con medidas de densidad aparente que permitieron confirmar porosidades inferiores al 20%. En algunas muestras se observó la coexistencia de amplias diferencias de tamaño de grano que ocasionaron variaciones en las respuestas ante la aplicación de campos eléctricos y magnéticos. El sistema de espectrometría de dispersión de energía de rayos X (EDS) acoplado al SEM, facilitó el establecimiento de la composición efectiva de las muestras de acuerdo con el porcentaje estequiométrico de cada elemento químico en cada material. Las medidas del parámetro magnético dependiente de la temperatura y de magnetización en función del campo aplicado, revelaron comportamientos paramagnéticos, ferromagnéticos y ferrimagnéticos en varias composiciones. Las técnicas de caracterización eléctrica de corriente-voltaje (I-V) y de resistividad en un rango amplio de temperatura (desde 60 K hasta 400 K, aproximadamente) pusieron en evidencia comportamientos de tipo semiconductor (alta resistividad a temperatura ambiente), semiconductor-termistor (baja resistividad a temperatura ambiente), mecanismos de transporte eléctrico donde intervienen polarones, tipo Mott (VRH) y tipo Efros-Shklovskii (ES) y que suministraron el cálculo de la energía de activación de cada mecanismo en algunas muestras. Medidas de permitividad en función de la temperatura con frecuencias constantes corroboraron los resultados de transporte eléctrico y mostraron relajaciones tipo Debye y Maxwell-Wagner en las muestras con más alta resistividad, con las cuales también a partir de curvas de Arrhenius se obtuvieron las energías de activación y se pudo deducir la probabilidad de transiciones de carácter eléctrico o magnético. Estos materiales tipo perovskita exhibieron una amplia gama de resistividades, correlacionadas con el gap de energía óptico obtenido en algunas muestras. La coexistencia de parámetros magnéticos y eléctricos a temperaturas similares sugirieron la existencia de acoplamientos magneto-eléctricos (algunos corroborados con cálculos de polarización a través de medidas de corriente piroeléctrica), así como la coexistencia de comportamientos semiconductores y ferromagnéticos a temperatura ambiente que potencializan eventuales aplicaciones propias de tecnologías inmersas en la industria de la espintrónica, de grabación de información, de sensores magnéticos y de temperatura, entre otras. (Texto tomado de la fuente) The crystalline structure of the new complex perovskites of the RAMOx (R = La, Nd, Sm, Eu; A = Sr, Bi; M = Ti, Mn, Fe) family and their subfamilies differ in their properties due to the fact that the elements that make them up when coupled create bonds that despite crystallizing in the same space group Pnma or Pbnm (# 62), show slight changes caused by the magnetic, electrical, ionic radio characteristics and by the ionic or covalent coupling of the different chemical elements that compose them, in addition to small differences in the atomic positions and reticular parameters in the structure with the majority phase found (98% purity), which at the same time leads to differences due to distortions or inclination of their B-O6 octahedra, which, having been exposed to different mechanical, electrical, magnetic or thermal stimuli, give rise to characteristic properties of each of the seven stoichiometric formulas synthesized and subsequently analyzed in this document. Polycrystalline samples were produced by the solid-state reaction synthesis method. During the different sintering stages, the crystalline evolution was obtained with the disappearance of the reflections of the precursor oxides from which the samples were synthesized. The Rietveld refinement with the use of GSAS software allowed to obtain the structure in which each compound crystallized and its crystallographic and reliability factors. The microstructural study through images obtained by scanning electron microscopy (SEM) showed a good degree of compaction of the grains, a result compared with apparent density measurements that allowed to confirm porosities lower than 20%. In some samples the coexistence of wide differences in grain size that caused variations in the responses to electrical and magnetic stimuli was observed. The X-ray energy dispersion spectrometry (EDS) system coupled to the SEM, facilitated the establishment of the effective composition of the samples according to the stoichiometric percentage of each chemical element in each material. Measurements of the temperature-dependent magnetic parameter and of magnetization as a function of the applied field, revealed paramagnetic, ferromagnetic and ferrimagnetic behaviors in various compositions. The electrical characterization techniques of current-voltage (I-V) and resistivity in a wide range of temperature (from 60 K to 400 K, approximately) showed behaviors of the semiconductor type (high resistivity at room temperature), semiconductor-thermistor (low resistivity at room temperature), electrical transport mechanisms involving polarons, Mott type (VRH) and Efros-Shklovskii type (ES) and that provided the calculation of the activation energy of each mechanism in some samples. Measurements of permittivity as a function of temperature with constant frequencies corroborated the electrical transport results and showed Debye and Maxwell-Wagner type relaxations in the samples with the highest resistivity, with which the activation energies were also obtained from Arrhenius curves and the probability of transitions of an electrical or magnetic nature could be deduced. These perovskite-type materials exhibited a wide range of resistivities, correlated with the optical energy gap obtained in some samples. The coexistence of magnetic and electrical parameters at similar temperatures suggested the existence of magneto-electrical couplings (some corroborated with polarization calculations through measurements of pyroelectric current), as well as the coexistence of semiconductor and ferromagnetic behaviors at room temperature. All this allows to visualize possible applications in technologies immersed in the spintronics industry, information recording, magnetic and temperature sensors, among others. (Text taken from source) MINCIENCIAS, por medio de la convocatoria del Departamento Administrativo de Ciencia, Tecnología e Innovación (Convocatoria Becas Nacionales 617-Colciencias) En el estudio de los materiales cerámicos tipo Perovskita analizados en el documento se encontraron propiedades de semiconductividad magnética, sensores de temperatura , grabación de información y Multifuncionalidad. Útil para ser aplicados en nuevas tecnologías. Doctorado Doctorado en Ingeniería - Ciencia y Tecnología de Materiales Se usó el método científico en el que se hizo observación sistemática durante la síntesis y caracterización de los materiales cerámicos tipo Perovskita; medición estructural por medio de DRX, morfológica y composicional por medio de MEB y EDS y de algunas características eléctricas, ópticas y magnéticas. Se experimentó durante las diferentes etapas y se formularon diferentes metodologías y rutas que llevaron a contante análisis de las propiedades encontradas, lo que también conllevó a modificar en algunos momentos aspectos de la hipótesis inicial planteada.​ Ciencia y Tecnología de Materiales Cerámicos y Compuestos Para las mediciones eléctricas se usó un equipo diseñado por el autor que contiene: cableado coaxial blindado y celda con cableado interno blindada con aluminio para evitar señales parásitas durante la medición, celda criogénica acoplada con adhesivo de Plata (Ag) entre el dedo frio y la lámina de soporte de la muestra en medición, que permite conductividad térmica.

We study a new diluted magnetic semiconductor system based on the spin of the ionized acceptor Cr$^+$. We show that the negatively charged Cr$^+$ ion, an excited state of the Cr in II-VI semiconductor, can be stable when inserted in a CdTe quantum dot (QD). The Cr$^+$ attracts a heavy-hole in the QD and form a stable hole-Cr$^+$ complex. Optical probing of this system reveals a ferromagnetic coupling between heavy-holes and Cr$^+$ spins. At low temperature, the thermalization on the ground state of the hole-Cr$^+$ system with parallel spins prevents the optical recombination of the excess electron on the 3$d$ shell of the atom. We study the dynamics of the nano-magnet formed by the hole-Cr$^+$ exchange interaction. The ferromagnetic ground states with M$_z$=$\pm$4 can be controlled by resonant optical pumping and a spin relaxation time in the 20 $\mu$s range is obtained at T=4.2 K. This spin memory at zero magnetic field is limited by the interaction with phonons.

Ferromagnetic semiconductors with structural flexibility are an indispensable feature for future flexible spin-electronic applications. In this case, we introduce magnetic ingredients into an organic semiconductor, namely, pentacene, to form a ferromagnetic organic semiconductor (FOS). The first observation for ferromagnetic Ni-doped pentacene semiconductors at room temperature in the field of semiconductor spintronics is reported in this article. To date, the mechanism of FOSs with ferromagnetism is not understood yet, especially when their Curie temperature is enhanced above room temperature. Here, we demonstrate dopants of Ni atoms and the modulation of the growth temperature in the FOS films to achieve room-temperature ferromagnetic properties in a series of FOS films, one of which has a maximum coercivity of 257.6 Oe. The spin-exchange interaction between a Ni atom and a pentacene molecule is detected through the magnetic hysteresis obtained using a superconducting quantum interference device magnetometer. We verify the effectiveness of this spin coupling through magnetic force microscopy, Raman spectroscopy, scanning Kelvin probe microscopy, and theoretical simulation. A model for the indirect spin coupling between Ni atoms is proposed for the mechanism of room-temperature ferromagnetic ordering of spins due to the exchange force indirectly. We believe that the π-electrons of pentacene molecules at the triple state for this model can support the spin coupling of electrons of Ni atoms. Our findings facilitate the development of brand-new spintronic devices with structural flexibility and room-temperature ferromagnetism.

One of the most attractive characteristics of diluted ferromagnetic semiconductors is the possibility to modulate their electronic and ferromagnetic properties, coupled by itinerant holes through various means. A prominent example is the modification of Curie temperature and magnetic anisotropy by ion implantation and pulsed laser melting in III–V diluted magnetic semiconductors. In this study, to the best of our knowledge, we performed, for the first time, the co-doping of (In,Mn)As diluted magnetic semiconductors by Al by co-implantation subsequently combined with a pulsed laser annealing technique. Additionally, the structural and magnetic properties were systematically investigated by gradually raising the Al implantation fluence. Unexpectedly, under a well-preserved epitaxial structure, all samples presented weaken Curie temperature, magnetization, as well as uniaxial magnetic anisotropies when more aluminum was involved. Such a phenomenon is probably due to enhanced carrier localization introduced by Al or the suppression of substitutional Mn atoms.

The experimentally observedd0-magnetism and its subsequent attribution to the presence of structural and topological defects has opened the way for engineering the magnetic properties of diluted magnetic semiconductors (DMSs) and transition metal oxides (TMOs). Doping and codoping constitute the most commonly used processes (either experimentally or theoretically) for developing and studying this type of defect-induced magnetism. The focus of the present review is to highlight the basic features of the defect magnetism which have been observed over diverse systems, while emphasizing the local, holistic and synergistic response of the host materials to their doping and investigating their role in the development of the magnetic coupling (MC) that is developed among the magnetic dopants.Ab initiocomputational results elucidate the local aspects of the MC (charge and spin transfers between dopants and their first nearest neighboring anion ligands) and their relation with holistic processes which are reflected in the band structure, and the shifts of both thed- andp-band centers of the doped material (compared to the undoped one). In view of these results the MC between the magnetic dopants is framed within the newly proposed successive spin polarization and the defect-induced defect-mediated models. The similarities found in the magnetic characteristics between the codoped DMSs/TMOs and the magnetic multilayer systems lends further support to these models which introduce new contributions to the MC that are competitive with the existing classical ones (superexchange, double exchange,s-d&p-dcouplings etc).

Recently lot of research work is being aimed towards introducing electron spin as a new dimension in semiconductors that will provide faster and more efficient microelectronic devices. In t...

For the first time, quaternary chalcogenide CuNi2InS4 nanocrystals with a wurtzite structure have been designed and fabricated as a new magnetic semiconductor. The phase structure analysis suggests that the synthesized wurtzite CuNi2InS4 phase has a disordered structure in which Cu+, Ni2+, and In3+ ions share the same lattice site of the unit cell with a random cation distribution. The prepared CuNi2InS4 nanocrystals have uniform bullet-like morphology, small size distribution, good monodispersity, and high crystallinity. The magnetic properties investigation reveals that the wurtzite CuNi2InS4 nanocrystals can exhibit a weak ferromagnetic moment with the blocking temperature at around 13 K thanks to the disordered wurtzite structure and the high content of magnetic Ni2+ ions. As for the semiconducting properties, the as-obtained wurtzite CuNi2InS4 nanocrystals show a strong and broad visible light absorption and have a direct bandgap of 1.45 eV. Due to their favorable optical properties, the fabricated t...

The results of the study of the spectral and relaxation parameters of 63.65Cu nuclear magnetic resonance (NMR) in a local field in natural samples of the semiconductor mineral chalcopyrite (CuFeS2), which is characterized by a strong interplay of magnetic and electronic properties, are presented. The main attention was paid to the determination of the mechanism of nuclear spin–lattice relaxation. The well-resolved quadrupole structure of the 63.65Cu NMR spectrum allowed us to investigate the kinetics of nuclear magnetization recovery for both Cu isotopes. The magnetic mechanism of the spin–lattice relaxation of the nuclear spins of copper isotopes 63.65Cu in CuFeS2, due to fluctuations of the dipole local fields created by the electron spins of magnetic Fe3+ ions, has been determined.

There is a substantial amount of literature dealing with many aspects of synthesis and characterization of pure and doped binary compounds including Mn-doped ZnO which has been widely studied due to its superb properties as a dilute magnetic semiconductor (DMS).Aspects concerning doping limits for these compounds is an important stage in the search for new materials. Samples of Zn1-xMnxO nanocrystal were synthesized at temperatures of 180 °C and 200 °C using wet or liquid phase synthesis method. Dopant concentrations x=0.5, 1, 1.5, 2, 2.5, 5, 10, 20, 30, 40 and 50 per cent were studied. Powder x-ray diffraction (PXRD) patterns of the samples were analyzed with a view to determining the onset of secondary phases and hence the solubility limit of the dopant. The solubility limit for Mn in ZnO samples synthesized at temperature of 200 °C is realized at x

We have demonstrated the feasibility of doping CdCr2Se4 single crystals with Group III elements (Ga, In, and Al) during annealing and identified relationships between annealing conditions, the composition of annealing mixtures, and properties of the crystals. Annealing mixture compositions have been found that ensure the possibility of preparing CdCr2Se4 single crystals with a considerably increased Curie temperature. We have performed multistep annealing of particular samples, which has made it possible to understand the role of each mixture component.

Diluted magnetic semiconductors with the unique advantage of simultaneously manipulating the spin and charge of electrons possess potential applications in spintronics and quantum computing, which attracts long-term tremendous attention. It is pivotal and meaningful for practical application that room temperature ferromagnetism has been acquired successively in ZnO based diluted magnetic semiconductors. Although the unclear origin of ferromagnetism hampers their further development, there is a consensus that their magnetic properties are susceptible to materials preparation process. As an extreme condition with high-intensity energy, indirect contact and controllability, high magnetic field has been applied to various materials fabrication. Similarly, high magnetic field is employed in the preparation of ZnO based diluted magnetic semiconductors to adjust microstructural and magnetic properties, such as enhancing Curie temperature, inducing the transition from paramagnetism or diamagnetism to ferromagnetism, and improving ferromagnetism, while exploring the ferromagnetism mechanism from another perspective. In this brief perspective, recent study on the high magnetic field processed ZnO based diluted magnetic semiconductors is reviewed.

The structure and electronic and magnetic properties of SnSe monolayer doped with transition-metal (TM) atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) were investigated using first-principles calculations. It is found that TM atoms can substitute either Se atoms (TM-Se) or Sn atoms (TM-Sn) to form thermodynamically stable systems. Semiconductor–metal or semiconductor–half metal transitions may be induced by TM atom doping, depending on the types of dopants and substituted atoms. The pristine nonmagnetic SnSe monolayers can be turned into magnetic systems by TM dopants. Especially, for TM-Se systems (TM = Sc, V, Mn and Fe) and TM-Sn systems (TM = V, Cr, Mn, Fe and Co), the monolayers become two-dimensional narrow-band diluted magnetic semiconductors (DMSs). Among the magnetic systems, TM-Se systems can exhibit either obviously enhanced (TM = Sc, Ti, V and Cu) or weakened (TM = Mn, Fe and Co) total magnetic moments, due to the strong interaction between the 3d-orbit of the dopant atoms and the 5p-orbit of the neighboring Sn atoms, while TM-Sn systems only exhibit slightly enhanced total magnetic moments, which shows the greater electronic tunability of Sn atoms than that of Se atoms. Our results may provide a platform for potential applications of SnSe monolayer-based spintronic materials.

While exploring novel magnetic semiconductors, the new phase Cr0.65Al1.35Se3 was discovered and characterized by both structural and physical properties. Cr0.65Al1.35Se3 was found to crystallize into orthorhombic CrGeTe3-type structure with space group Pnma (no. 62). Vacancies and mixed occupancies were tested, and the results show that one of the 4c sites accommodates a mixture of Cr and Al atoms, while the other 4c site is fully occupied by Al atoms. Unique structural features include a T-shaped channel network created from the edge-sharing Cr/Al@Se6 and Al@Se4 polyhedra and a zipper effect of the puckered Se atoms inside the columnar channels. The round peak observed in the temperature-dependent magnetic susceptibility (χg) plot at ∼8(1) K corresponds to the antiferromagnetic-type transition in Cr0.65Al1.35Se3. However, the positive θCW indicates an additional ferromagnetic interaction, which is highly likely due to the complex magnetic structure arising from the mixed Cr/Al occupancies on the 4c site. Electrical resistivity measurements confirm that Cr0.65Al1.35Se3 is a semimetal with a positive magnetoresistance. Here we present the characterization and determination of the crystal structure and physical properties for this new material.

polycrystalline CuxYyOz are made through solid state reaction. Ferromagnetism is found in this YCuO system at room temperature. The ferromagnetism quite probably originates from Cu2Y2O5 , the Copper Yttrium Oxide. The average magnetic moment per Cu2+ is estimated to be 0.04μB. Itinerant electron magnetism is a rational explaination for the observed ferromagnetism. The experiment shows that the excessive amount of Cu may lead more defects and further distortion in the lattice and decrease the exchange interaction. This reminds us that the Copper Yttrium Oxide is a substance not only should be avoided in fabricating YBCO superconductors but also should be considered as a potential substance of magnetic semiconductor.

I comparatively determine the electronic structures and magnetic properties of ScN doped with several transition metals (TM) by spin density functional theory using the Perdew-Burke-Ernzerhof (PBE) version of the generalized gradient approximation (GGA + U). The lattice parameters and volumes are modified by transition metals. Ti doping in ScN compound remains semiconductor with reduced band gap. (Sc, Cr)N, (Sc, Mn)N and (Sc, V)N are half metallic. (Sc, Co)N, (Sc, Fe)N and (Sc, Ni)N are characterized as metal. The magnetism is convinced from the hybridization of TM-d states with N-p states. The main contributors to this induced magnetism are the transition metal dopants. After the transition metal doping process, the ionic character of Sc–N bonds is reduced. Cr, Mn and V doping in ScN demonstrate the performance of the dilute magnetic semiconductor. Finally, this work sheds light on a central information of ScN doped with transition metals in regard to its technological applications.

A low cost self-powered UV Schottky photosensor uses as photoactive layer a Co2+: ZnO diluted magnetic semiconductors nanoparticles (DMS) is presented in this paper. Herein, for the first time, a high-performance UV photosensor is elaborated using Co2+: ZnO nanoparticles based on a low-cost polyol method. In addition to the optical band gap of ZnO, Cobalt can yield another optical absorption band associated to the Co+2 d-d (tethrahedral symmetry) crystal field transitions, which could enhance the total optical absorption and produce a high responsivity. Several characterization techniques such as XRD, TEM, FTIR, PL and diffuse reflectance (DF) spectroscopy are used in this study. The performance of our devices was evaluated upon exposing to UV light of wavelength 375 nm and at zero bias voltage. The device exhibits a sensitivity of 209.7 and a high responsivity about 5.5 103 mA/W under intensity of 7.6 mW. The response times (the rise and recovery times) of our device are 0.62s and about 1.65 s without any external bias, respectively. Our self-powered PD shows higher detectivity about 1.3 1013 Jones, compared to the UV PD in other works. Such high responsivity and detectivity lead the Co2+: ZnO PD to have low noise spectral density of 10 − 24 A2/Hz and low noise equivalent power of 2.6E-11 W Hz−1/2. This study proposes an original process for the fabrication of low cost self-powered PDs with high performance and zero power consumption on a large-scale.

Exploring two-dimensional (2D) graphene-like materials with magnetic characteristics has attracted intense research interest. Here, based on spin-polarized density functional theory calculations, the tunable electronic structures, half-metallicity and optical properties can be realized in the 2D monolayer MoSe2 by Fe-NM (NM=B, C, N) codoping. The results indicate that the Fe-doping and Fe–B codoping exhibit a robust magnetic half-metallicity, which can be attributed to that the electrons partially occupy the bonding state consisting of Fe e1 and Fe a1 states at the Femi level (EF). The Fe–N codoping exhibits a magnetic semiconductor character due to the strong hybridization between Fe dxy, dz2 states and N pz state. However, the Fe–C codoping shows a non-magnetic ground state due to the effective charge compensation between Fe and C atoms. The Fe-NM codoping can effectively tune the optical properties of monolayer MoSe2 by the introducing of impurity levels near the EF. A stronger and wider absorption in the visible region of 1.8–3.2 eV is observed, which is in favor of the visible light devices and potential solar absorbers. The distinctive magnetic half-metallicity, electronic and optical properties for the Fe-NM co-doped monolayer MoSe2 have great prospects in the fields of spintronics, opto-electronics and magneto-optics devices.

Layered dilute magnetic semiconductors are expected as promising candidates for next-generation electric devices, however, the low saturation magnetization limits their applications. Doping of semiconductors can effectively tune the magnetic and optical properties, which further influence on spintronic and optoelectronic applications. The discovery of layered materials opens a new door for spintronic application due to their unique properties. Here, the layered Gd3+ doped SnO crystals are synthesized via a simple hydrothermal method, with morphologies ranging from square shapes to four-pointed star shapes. We investigated the UV–vis absorption spectra, photoluminescence spectra and magnetic characteristics of the samples. The as-obtained Gd3+ doped SnO crystals show robust ferromagnetism at room temperature. From the first-principles calculations results, the substitution Gd dopants and the O vacancies work together to introduce the ferromagnetism. Our results demonstrate the Gd3+ doping tunability of SnO, a ferromagnetic layered material, as a functional material for spintronics and optoelectronics.

Angle-resolved photoelectron spectroscopy (ARPES) is the main experimental tool to explore electronic structure of solids resolved in the electron momentum k . Soft-X-ray ARPES (SX-ARPES), operating in a photon energy range around 1 keV, benefits from enhanced probing depth compared to the conventional VUV-range ARPES, and elemental/chemical state specificity achieved with resonant photoemission. These advantages make SX-ARPES ideally suited for buried heterostructure and impurity systems, which are at the heart of current and future electronics. These applications are illustrated here with a few pioneering results, including buried quantum-well states in semiconductor and oxide heterostructures, their bosonic coupling critically affecting electron transport, magnetic impurities in diluted magnetic semiconductors and topological materials, etc. High photon flux and detection efficiency are crucial for pushing the SX-ARPES experiment to these most photon-hungry cases.

We present, in this paper, a non-conservative approach for building reliable magnetic field sensors based on the resistive and magnetoresistive responses of a varistor diode. These sensors can be built on a ceramic platform of a material which is a solid solution of the ilmenite–hematite consisting of 55 moles% ilmenite, FeTiO3, and 45 mole% of hematite, Fe2O3. This material is abbreviated as IHC 45. These sensors would be suitable for many applications in which a semiconductor Hall effect sensor is currently used. In addition, our ceramic sensors would be suitable for applications in high temperature, energy exploration and well logging, and radiation-dominant environments. The resistive mode sensor is expected to operate reliably and efficiently over the range of 0 $\text{m}\Omega $ /Oe at 0.5 mA which drops to a value of 24.2 $\text{m}\Omega $ /Oe at 2 mA. In the magnetoresistive mode, the sensor has the sensitivity of $142.6~\Omega $ /ln(Oe) and it is 15.6 $\text{m}\Omega $ /Oe at 2 mA. The magnetoresistive mode device also exhibits at room temperature a relatively large magnetoresistive ratio (MR%) of 57% at the modest field of just 4000 Oe making it potentially an attractive candidate for applications in spintronics and magneto-electronics.

Zn(1−x)CoxO nanoparticles with (x = 0.05, 0.10, 0.15 and 0.20) were prepared by combustion method. Here we report our findings on electrical properties carried out on these materials from room temperature to 500 °C. Thermopower investigations carried out on the materials resulted in Seebeck coefficient showing a transition from positive to negative values with ‘x’ dependent enhancements. The material that exhibits a p-type semiconductor character at room temperature translates into an n-type of semiconductor at higher temperatures beyond 90 °C marked by a first order transition. Electrical resistivity and the activation energy being interrelated are seen to decrease with rising temperature due to increase in charge carrier concentration. Dielectric constant (e) and dielectric loss (tan δ) investigated as a function of frequency showed nearly exponential decline in their values with increasing frequency for all the samples. However temperature dependent ‘e’ and ‘tan δ’ show a peaking behaviour at lower temperatures with increasing trend at higher temperature as a result of increase in dielectric polarization. The DMS materials being ferromagnetic at room temperature are good temperature dependent semiconductors with high dielectric constant.

This paper considers mechanophysical methods (shear under pressure and explosive loading) developed for producing high-density optical nanoceramics based on some oxide magnetic semiconductors and their optical properties. Advantages of these methods are the simplicity of implementation, a combination of nano-grinding and compaction of material in a single process, obtaining high-density (∼99%) stable materials, and the absence of external impurity. It is shown that copper oxide nanoceramics can be used as solar energy absorbers and iron-yttrium garnet nanoceramics as an optical element in electromagnetic radiation modulators.