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The magnetic properties of the dilute magnetic semiconductor (DMS) are due the existence of two competing interactions, a direct ferromagnetic interaction and an indirect antiferromagnetic interaction. This is well established in the Zn1-xMnxO DMS, but is controversy in the Zn1-xCoxO DMS. To gain insights, a series of Co-substituted ZnO NRs (x = 0,...
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Magnetic semiconductors are at the core of recent spintronics research endeavors. Chemically doped II-VI diluted magnetic semiconductors, such as (Zn1-x Cr x )Te, provide a promising platform in this quest. However, a detailed knowledge of the microscopic nature of magnetic ground state is necessary for any practical application. Here, we report on...
Here we report the first-principle study of a bulk oxide diluted magnetic semiconductor (DMS) La 0.75 Ca 0.25 Cu 0.75 Mn 0.25 SO and its parent LaCuSO. As a wide band gap p-type oxide semiconductor, LaCuSO system satisfies all the conditions forecasted theoretically to be a room temperature DMS, which is important for formation of high temperature...
Citations
... Oxide-based DMSs are typically slightly doped with 3d transition metals. ZnO semiconductor, characterized by a wide band gap, becomes an attractive host metal oxide, exhibiting ferromagnetism above room temperature when doped with 3d transition metal (TM) ions such as Ni 2+ , Fe 2+ , Mn 2+ , Co 2+ , etc., [1][2][3][4][5][6][7][8][9][10]. The doping content, technique, conditions, and subsequent treatment of the doped samples can significantly alter their morphological, structural, optical, and ferromagnetic properties compared to the host ZnO [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. ...
... ZnO semiconductor, characterized by a wide band gap, becomes an attractive host metal oxide, exhibiting ferromagnetism above room temperature when doped with 3d transition metal (TM) ions such as Ni 2+ , Fe 2+ , Mn 2+ , Co 2+ , etc., [1][2][3][4][5][6][7][8][9][10]. The doping content, technique, conditions, and subsequent treatment of the doped samples can significantly alter their morphological, structural, optical, and ferromagnetic properties compared to the host ZnO [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Cobalt (Co), due to its smaller ionic radius of 0.058 nm compared to Zn's 0.060 nm, offers better solubility in ZnO, favoring doping at the Zn 2+ site. ...
... Cobalt (Co), due to its smaller ionic radius of 0.058 nm compared to Zn's 0.060 nm, offers better solubility in ZnO, favoring doping at the Zn 2+ site. Among the transition metal-doped ZnO nanoparticles (NPs), Co-doped ZnO NPs have shown comparatively better optical properties and ferromagnetic behavior [1][2][3][4][5][6][7][8][9]. It appears that Co-doping in ZnO results in a promising injection of spin and carrier, making it suitable for applications in DMSs [6][7][8][9]. ...
... The magnetic properties of nanostructured ZnO are strongly influenced by the type of defects and dopants in the sample [11]. ZnO based diluted magnetic semiconductors (DMSs) have attracted the researchers due to its possible applications in spintronic devices [12][13][14][15]. ...
Properties of chemically synthesized Zn1-xGdxO (x = 0.01, 0.03 and 0.05) nanorods were explored through microstructural, morphological, toxicity and magnetic characterizations. Hexagonal wurtzite structure of all the samples without any impurity phases was confirmed by X-ray diffraction characterization. The micrographs of transmission electron microscope and field emission scanning electron microscope revealed the rod shape morphology of the samples. A systematic evolution of room temperature ferromagnetism of ZnO nanorods with increasing Gd doping content was observed. Gd doped ZnO nanorods showed narrow-spectrum antibacterial activity against the most opportunistic Gram-positive pathogen bacterium, S. aureus as compared to commercial ZnO. From cytotoxicity assessment with Caenorhabditis elegans and Danio rerio, the samples were non-toxic or showed little toxicity at the highest concentration tested (100 µg/mL) except for 1% Gd doped ZnO. Our study demonstrates the possible usefulness of the materials in spintronic, magnetic media device as well as bio-medical applications.
... Composition design of the DMS is mainly based on doping of transition metal (TM) oxides, or sometimes rare earth oxides, into II-VI and III-V compound semiconductors. The exchange interaction between delocalized charge carriers (electrons or holes) in the host semiconductor and localized d-spins of the dopant is expected to bring about global ferromagnetism in the entire lattice [9]. Among semiconductor hosts, ZnO gained tremendous attentions for fabrication of DMS materials owing to several attractive properties. ...
Citrate sol–gel method has been employed for synthesis of Zn1˗x˗yMnxCryO nanomaterials. Binary Zn0.9Mn0.1O and Zn0.9Cr0.1O nanomaterials were prepared and their optical and magnetic properties were investigated as reference compositions for the individual behavior of both of Mn- and Cr doping, respectively. The synthesized nanoparticles were analyzed using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), ultraviolet–visible (UV–Vis) spectroscopy and vibrating sample magnetometer. For low Mn–Cr-codoping contents, i.e., 2 and 4%, XRD revealed formation of single-phase ZnO nanoparticles in the wurtzite type hexagonal lattice, whereas 10% doping concentration, either Mn- or Cr-single doping or codoping, resulted in formation of wurtzite ZnO as a major phase with ZnMnO3 or/and ZnCr2O4 secondary phases. From XRD and HRTEM, the produced nanomaterials have average crystallite sizes ranged from 15 to 35 nm. Applying Kubelka–Munk function, optical band gap energy (Eopt) was determined. Eopt of single Mn- and Cr-doped ZnO increased than that of bulk ZnO mainly due to Burstein–Moss effect, whereas it decreased in the codoped Zn1−x−yMnxCryO because of the negative and positive corrections in the conduction and valence band, respectively, brought about by alteration of the sp–d exchange interactions between the band electrons and the localized d-electrons of the Mn2+ and Cr3+ ions. Magnetization measurements indicated that Cr induced the paramagnetism, while Mn induced the RT ferromagnetism in the synthesized Zn1−x−yMnxCryO nanoparticles. The ferromagnetic Zn1−x−yMnxCryO compositions could be potential candidates for Mn–Cr-codoped ZnO-based DMS nanoparticles.
... We did this in ref. [9] where we assumed that in certain doping ranges, the increase in the Mn doping would cause the change in the antiferromagnetic exchange interaction to be greater than the change in the ferromagnetic exchange interaction. In a recent paper [13], the authors observed that increasing in the magnetic moments of the Co-doped DMS is due to the fact that the change in the antiferromagnetic exchange interaction is smaller than the change in the ferromagnetic exchanges interaction as more Co is doped in. ...
... This was interpreted as showing that the interaction between the Mn ions was antiferromagnetic. Robkhob, Tang and Thongmee [13], found that substitution of more Co ions did not change the ferromagnetic nature of the net interactions, i.e., the increase in the Co substitution could not cause the net interaction to switch sign. However, in their study on the effects of TM doping of ZnO NP's, Balti et al., [20] where the net interaction changes with the level of the Ni doping. ...
... This could cause a change in the sign of the net interaction between the Ni ions. Following the steps taken in ref. [13] in which the Co-doped ZnO DMS's were considered, we find the first order correction to the energy due the interaction between the Ni ions to be -2c 2 J < S Ni > 2 where < S Ni > is the configuration averaged spin of the Ni ion. The magnetic moment TM ion in the molecular field approximation is proportional to the configuration average of the spin of that ion. ...
Ni doped ZnO nanoparticles (NP’s) was fabricated by hydrothermal method. XRD result investigated that all peaks could be indexed to hexagonal wurtzite structure of ZnO NP’s with no impurity phases. The values of saturation magnetization when expressed in terms of emu/g increases as the doping level increases but decreases when MS is expressed in terms of µB/Ni ion. PL spectra exhibit an increased blue shift as more Ni doping. The blue shifts of the peak in the visible light spectrum of the PL emissions of the Ni doped ZnO NP’s also indicate that more singly ionized oxygen vacancies are being created. The combination of their being more polarized d electrons available and more singly ionized oxygen vacancies around which the d electrons of the Ni²⁺ ions can localize to form the BMP’s would lead to an increase in the antiferromagnetic contribution to the net exchange interaction between Ni ions to increase.
... In the recent several decades, low dimensional magnetic materials for instance nanowires, nanotubes, nanorods, nanosheets and nanoparticles... have been broadly studied theoretically and experimentally, to understand their special physical performances [1][2][3][4][5][6][7]. But they are also being studied for their potential applications as nanomaterials with specific functionalities [8][9][10][11]. ...
The magnetization loops of a hexagonal spin-3/2 Ising nanotube are examined in the framework of the effective field theory with correlations, based on the differential operator technique. We have explored the impacts of distinctive exchange couplings on key physical parameters such as Phase diagram, magnetization, susceptibility, internal energy, and specific heat. Some special phenomena are inspected in terms of thermal effects or crystal-field when the other inherent parameters of the nanotube are adjusted. Furthermore, We have found that the exchange couplings, the temperature, and single-ion anisotropy have a strong impact on the shape and the number of hysteresis loops as well as on the coercive field and magnetization behaviors.
Keywords :
Spin-3/2 Ising nanotubeExchange interactionsSingle-ion anisotropyHysteresis loopsEffective field theoryPhase diagramMagnetization plateaus
Impacts of hydrogen annealing on crystallographic characterization, electronic structure, and optical, photocatalytic, and magnetic properties of polycrystalline Zn1−xCoxO (x = 0.01–0.06) samples have been considered. Structural analyses based on powder X-ray diffraction, Rietveld refinement, and Raman spectroscopy prove all materials having the P63mc wurtzite-type structure. The Co-doping and hydrogenation changed the concentration of Zn– and O–related defects whose energy levels occupy the band gap. This also enhanced photocatalytic performance of hydrogenated samples with x > 0.02. X-ray and UV–Vis absorption analyses indicate the substitution of Co²⁺ for Zn²⁺ in the wurtzite-type ZnO lattice, leading to irregularly changed the unit-cell parameters. While all the as-prepared samples are paramagnetic, the hydrogenated ones exhibit weak ferromagnetism. Ferromagnetic (FM) ordering increases when x increases, particularly for x ≥ 0.02. According to the results achieved from studying crystalline and electronic structures, we believe that oxygen-vacancies-mediated interactions between Co²⁺ ions and H–Co–H exchange dimers enhanced FM ordering in hydrogenated Zn1−xCoxO. Computational investigations have also indicated that the magnetization value of H–Zn1−xCoxO is influenced by the positioning of the H dopant, meaning that the couplings between Co and H play an essential role in establishing FM order in H–Zn1−xCoxO.
Graphical Abstract
Co content plays a crucial role in the magnetic and electric properties in Co doped ZnO (ZnO:Co) films. In this work, the method of RF source-assisted molecular-beam vapour deposition was used to prepare ZnO:Co films with various Co contents. The doped Co²⁺, the metal Co, and the oxygen vacancies (Vo) were found in the deposited films. The surface roughness and the crystalline size of the ZnO:Co films also increased by using bigger Co content. The prepared ZnO:Co films show n-type conductivity and room temperature ferromagnetism. By increasing the Co content, the content of the metal Co exceeded that of the doped Co²⁺ gradually, which led to the higher electric conductivity, carrier concentration, mobility, and saturation magnetization.
The hydrothermal process was used to prepare Mn3O4/x%GO nanocomposites (NC’s) having different ratios of the Mn3O4 nanoparticles (NP’s) on the surface of graphene oxide (GO) sheet. SEM image showed that the Mn3O4 NP’s were distributed over the surface of GO sheet. HRTEM images exhibited the lattice fringe arising from the (101) plane of the Mn3O4 NP’s having the interplanar d-spacing of 0.49 nm decorating on the surface of GO. The electronic absorption spectra of Mn3O4/x%GO NC’s also show broad bands from 250 to 550 nm. These bands arise from the d–d crystal field transitions of the tetrahedral Mn³⁺ species and indicate a distortion in the crystal structure. Photo-catalytic activity of spinel ferrite Mn3O4 NP’s by themselves was low but photo-catalytic activity is enhanced when the NP’s are decorating the GO sheet. Moreover, the Mn3O4/10%GO NC’s showed the best photo-catalytic activity. This result comes from the formation of Mn–O–C bond that confirm by FT-IR. This bond would facilitate the transfer of the photoelectrons from the surfaces of the NP’s to the GO sheets. PL emission which is in the violet–red luminescent region shows the creation of defects in the fabricated Mn3O4 NP’s nanostructures. These defects create the defect states to which electrons in the VB can be excited to when the CB. The best degradation efficiency was achieved by the Mn3O4 NP’s when they were used to decorate the GO sheets in the Mn3O4/10%GO NC’s solution.
Highlights
Lattice fringe of Mn3O4 with an interplanar d-spacing of 0.49 nm for (101) plane.
Photocatalytic activity of spinel ferrite Mn3O4 nanoparticles by itself is low.
Number of photoelectrons created depends on number of Mn3O4 on a given area of GO
The bonding of the Mn3O4 to the GO sheet would be though a Mn–O–C junction.
The degradation processes were accelerated by Mn3O4/10%GO nanocomposites
Graphic abstract
