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Investigation of photocatalytic, electrochemical, optical and magnetic behaviors of rare-earth double perovskites using combustion synthesized Gd2NiMnO6 nanostructures in the presence of different saccharides
摘要： This paper reports combustion synthesis of Gd2NiMnO6 nanostructures (GNMO NSs), for the ?rst time, through reaction between metal nitrates in the presence of different saccharides, as capping and reducing agents. Analysis of XRD, FT-IR, EDS, along with TEM and SEM images and also VSM and DRS spectra were applied to study the NSs. The VSM showed an antiferromagnetic behavior. The DRS spectroscopy ascertained semiconducting behavior of GNMO NSs with Eg ? 3.05 eV for optimum sample prepared in the presence of glucose at 1000 (cid:2)C. The CV was used to investigation of electrochemical property of the NSs. For the ?rst time, the photocatalytic behavior of the GNMO NSs was evaluated, using the degradation of organic dyes under UV irradiation. The photodegradation of EDT was almost similar to that of ES, except for initial times of the irradiation. The degradation percentage of EBT and ES in the presence of GNMO NSs was large, whereas that of MV was little in the time range.
关键词： Direct band gap,Photocatalysis,Antiferromagnetism,Gd2NiMnO6,Combustion,Nanostructures
更新于2025-09-23 15:21:21
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Can one introduce long range ferromagnetism by doping transition metal in wide band gap semiconducting ZnO?
摘要： In this report, we present a systematic study of magnetic behavior of transition metal (TM = Fe or Cu) doped ZnO and co-doped (Cu, Fe) ZnO nanoparticles. All the samples show antiferromagnetic (AFM) like inverse susceptibility at low temperatures. In all the samples AFM Curie-Weiss temperature TAF M increases with increase in TM ion concentration indicating enhanced antiferromagnetic correlation upon TM doping. We observe a crossover from antiferromagnetic correlation state to ferromagnetic correlation around temperature (T) 100 - 150K. We shall try to explain all the experimental observations by invoking the role of oxygen vacancies, valency of transition metal ions, formation and interaction between bound magnetic polaron (BMP) and their melting in ZnO matrix. Even though we observe ferromagnetic correlation around room temperature in all these samples from the inverse magnetic susceptibility data, but no true long range ferromagnetic transition was observed in magnetization down to lowest measured temperature of 5K. Our study indicates the di?culties in achieving long range ferromagnetism arising due to the formation of BMPs upon lowering the temperature where these BMPs get antiferromagnetically correlated due to superexchange interaction occurring in transition metal doped wide band gap semiconducting ZnO matrix.
关键词： Dilute magnetic semiconductor,Bound magnetic polaron,Antiferromagnetism,Transition metal doping,ZnO,Ferromagnetism
更新于2025-09-23 15:21:21
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Valley polarization reversal and spin ferromagnetism and antiferromagnetism in quantum dots of the topological insulator monolayer bismuthene on SiC
摘要： The valley and spin polarizations associated with electronic transport in quantum dots of the large-gap topological insulator (TI) monolayer bismuthene on SiC are investigated in the linear response regime using a minimal tight-binding model that accurately describes the low-energy electronic band structure of this TI. It is found that for zigzag edges the electronic edge states are strongly valley polarized if the Fermi energy lies in the bulk energy band gap. We predict the edge-state valley polarizations to switch between valleys K and K (cid:2) as the Fermi energy varies from the top of the valence band to the bottom of the conduction band or if the direction of electric current through the dot is reversed. If the electrostatic potential in the dot is nonuniform, we predict that the valley polarization of an electron can reverse as it travels through the dot. The valley polarization reversal is due to the zigzag edge-state dispersion crossing the center of the Brillouin zone that separates valleys K and K (cid:2) and is therefore predicted to be a general phenomenon. Although the spin polarization within the edge states is ferromagnetic, as expected for spin Hall devices, our calculations reveal the out-of-plane component of the spin polarization of the bulk valence band scattering states to be antiferromagnetic, and the direction of the out-of-plane component of the Neel vector to depend on whether the electronic accumulation belongs primarily to valley K or K (cid:2).
关键词： quantum dots,ferromagnetism,bismuthene,topological insulator,spin polarization,antiferromagnetism,SiC,tight-binding model,valley polarization
更新于2025-09-23 15:19:57
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First-principles investigation on the interlayer doping of SnSe2 bilayer
摘要： Using density functional theory calculations, we systematically investigated the effects of numbers and types of transition metals (TM) on the magnetic property of SnSe2 bilayer nanosheet. Our results revealed that, when one TM is introduced into the interlayer, the magnetic moment induced by the Co and Ni is tiny while it is largely strengthened with the doping of V, Cr, Mn, and Fe. When two TMs are inserted into the interlayer, Vand Cr make the system change into a weak antiferromagnetism (AFM) state while Mn-, Fe-, Co-doped systems display a weak ferromagnetism (FM) ground state. These FM states have the magnetic moments which double those of the one TM–doping systems. With the TM numbers further increasing to four, the robust AFM and FM features appear with the doping of Fe and Mn, respectively. Ni cannot induce any magnetism whatever the numbers of Ni are filling in. Interestingly, with the increase of the numbers of dopants, transitions from FM to AFM and AFM to FM are predicted to be realized on Fe-SnSe2 and Cr-SnSe2 systems, respectively. This kind of transition may be important for the applications in spintronic devices.
关键词： Interlayer doping,Spintronics application,Density functional theory,Antiferromagnetism,Modeling and simulation,Ferromagnetism,SnSe2
更新于2025-09-10 09:29:36
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Emergent interlayer nodal superfluidity of a dipolar Fermi gas in bilayer optical lattices
摘要： Understanding the interplay between magnetism and superconductivity is one of the central issues in high-temperature superconductors. The recent experimental implementation of cold gases with highly tunable anisotropic interaction, especially in magnetic dipolar atoms or polar molecules, opens up a new thrust on exploring this interesting phenomenon. Here we report a mechanism to drive the interplay between magnetism and superfluidity through engineering the spatially anisotropic interaction via considering loading pseudospin-1/2 dipolar Fermi atoms in bilayer optical lattices. Surprisingly, we find that the weak interlayer interaction can lead to the coexistence of superfluidity and antiferromagnetism at low temperatures for the half filling case. It is distinguished from the usual scheme by doping an antiferromagnetic Mott insulating parent to access high-Tc superconductivity, where at half filling there is no coexistence of superconductivity and magnetism at low temperatures due to the absence of the superconductivity. Furthermore, the interlayer superfluid possesses an unexpected nodal structure, which is reminiscent of the nodal high-Tc superconductivity but differs in origin.
关键词： antiferromagnetism,bilayer optical lattices,dipolar Fermi atoms,superfluidity,interlayer interaction,superconductivity,magnetism,nodal structure
更新于2025-09-09 09:28:46
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Poling of an artificial magneto-toroidal crystal
摘要： Although ferromagnetism is known to be of enormous importance, the exploitation of materials with a compensated (for example, antiferromagnetic) arrangement of long-range ordered magnetic moments is still in its infancy. Antiferromagnetism is more robust against external perturbations, exhibits ultrafast responses of the spin system and is key to phenomena such as exchange bias, magnetically induced ferroelectricity or certain magnetoresistance phenomena. However, there is no conjugate field for the manipulation of antiferromagnetic order, hindering both its observation and direct manipulation. Only recently, direct poling of a particular antiferromagnet was achieved with spintronic approaches. An interesting alternative to antiferromagnetism is ferrotoroidicity—a recently established fourth form of ferroic order. This is defined as a vortex-like magnetic state with zero net magnetization, yet with a spontaneously occurring toroidal moment. As a hallmark of ferroic order, there must be a conjugate field that can manipulate the order parameter. For ferrotoroidic materials, this is a toroidal field—a magnetic vortex field violating both space-inversion and time-reversal symmetry analogous to the toroidal moment. However, the nature and generation of the toroidal field remain elusive for conventional crystalline systems. Here, we demonstrate the creation of an artificial crystal consisting of mesoscopic planar nanomagnets with a magneto-toroidal-ordered ground state. Effective toroidal fields of either sign are applied by scanning a magnetic tip over the crystal. Thus, we achieve local control over the orientation of the toroidal moment despite its zero net magnetization.
关键词： ferrotoroidicity,antiferromagnetism,toroidal moment,ferromagnetism,nanomagnets
更新于2025-09-04 15:30:14