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dz2 Orbitals Mediated Bound Magnetic Polarons in Ferromagnetic Ce Doped BaTiO3 Nanoparticles and its Enriched Two Photon Absorption Cross Section
摘要： Enriched ferromagnetism and two photon absorption (TPA) cross section of perovskite BaTiO3 nanoparticles are indispensible for magnetic and optical data storage applications. In this work, the hydrothermally synthesized Ce doped BaTiO3 nanoparticles exhibit the maximum room temperature ferromagnetism (4.26×10-3 emu/g) at 4 mol% due to the increase of oxygen vacancies as evidenced by X-ray photoelectron, electron spin resonance spectroscopies and density functional theory (DFT) calculations. Hence, the oxygen vacancy constituted bound magnetic polaron (BMP) model has been invoked to explain the enhancement of ferromagnetism. BMP theoretical model indicates the increase of BMP magnetization (M0, 3.0 to 4.8×10-3 emu/g) and true spontaneous moment per BMP (meff, 4 to 9.88×10-4 emu) on Ce doping. DFT calculations show that BMPs mediate via Ti d orbitals leading to the ferromagnetism. Besides, it is understood that the magnetic moment induced by Ce at Ba site is higher than Ce at Ti site in the presence of oxygen vacancies. Open aperture Z-scan technique displays the highest TPA coefficient β (7.08×10-10 m/W) and TPA cross section σTPA (455×104 GM) at 4 mol% of Ce as a result of robust TPA induced excited state absorption. A large σTPA is attributed to the longer excited state lifetime τ (7.63 ns) of charge carriers created by oxygen vacancies and Ce ions which encounter several electronic transitions in the excited sub-states.
关键词： Ce doping,oxygen vacancies,bound magnetic polarons,two photon absorption,DFT calculations,Z-scan technique,BaTiO3 nanoparticles,ferromagnetism
更新于2025-11-19 16:56:35
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First principles study of electronic structures of Cd0.9375Co0.0625X (X?=?S, Se, Te) for magnetic, optical and thermoelectric device applications
摘要： The present article investigates the structural and electronic properties of Co doped (xCo = 6.25%) CdS/Se/Te diluted magnetic semiconductors to understand the optical and thermoelectric characteristics. The electronic properties, computed by applying generalized gradient approximation (GGA) and then modified Becke Johnson (mBJ) functional, are contrasted to identify the appropriate electronic parameters. The stable ferromagnetic states have been justified to arise due to the p-d hybridization that has been found responsible in inducing magnetic moments at the interstitial and at the non-magnetic sites. The computed direct band gap and the exchange constants (N0α and N0β) have suggested, respectively, the potential optical and spintronic device applications. The studied compounds operate within visible-ultraviolet energy range. The thermoelectric response improves with temperature, while deteriorated due to Co doping. The studied compounds exhibiting various significant physical properties evidence the potential consumption in various technologically important spintronic, optoelectronic and thermoelectric devices.
关键词： Optical properties,Ferromagnetism,Diluted magnetic semiconductors,Thermoelectric properties,mBJ potential
更新于2025-09-23 15:23:52
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Effects of Co Doping and Point Defect on the Ferromagnetism of ZnO
摘要： The effects of different doping proportions of Co doping and oxygen vacancies (VO) on the ferromagnetism of zinc oxide (ZnO) are controversial. To solve this problem, we investigated the effects of Co doping and point defects (VO, VZn, Hi, and Zni) on the ferromagnetism of ZnO through first-principle calculations by using generalized gradient approximation + U (GGA + U) under density functional theory. Results show that the closer the distance between Co and vacancies (VO or VZn), the lower the formation energy and the more stable the system will be. Co-doped ZnO with VO or VZn exhibits long-range ordered ferromagnetism and Curie temperature above the room temperature. Especially, Co-doped ZnO with VZn shows a half-metallic behavior, resulting in 100% conduction hole polarizability, which is highly beneficial for dilute magnetic semiconductors (DMSs) as a hole injection source. The ferromagnetism of Zn14CoO16 is caused by the double exchange effects among the electrons of the O–2p, Co–3d, and Zn–3d orbits mediated by the hole carriers after complexes were formed by the Co doping and Zn vacancy. Similarly, the origin of ferromagnetism in Zn15CoO15 is derived from the double exchange effects among the electrons of O–2p, Co–3d, and Zn–4s states mediated by the electron carriers after complexes were formed by the Co doping and O vacancy. In addition, the result shows that Co-doped ZnO with interstitial H (Hi) or Zn (Zni) is unfavorable for ferromagnetism and should be avoided experimentally.
关键词： First-principle,Co doping and point defect,Ferromagnetism,ZnO
更新于2025-09-23 15:22:29
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Ferromagnetism and Carrier Transport in n-type Diluted Magnetic Semiconductors Ge0.96?xBixFe0.04Te Thin Film
摘要： The structural, Hall effect, electronic transport, and magnetic properties of Ge0.96?xBixFe0.04Te epitaxial thin film as prepared by pulsed laser deposition technique were reported. X-ray diffraction patterns including linear scans and phi scans confirmed that all films are high quality epitaxy and crystallinity. With the substitution of high valence Bi for Ge element, we found that the previous carriers of hole were changed to electron, which was testified by the negative slopes obtained from the measurements of Hall effect under different temperatures. The electronic transports show a typical semiconductor behavior and can be understood by the small polaron hopping model because the lattice distortions increase the electron-phonon interaction. An obvious ferromagnetic properties occur in the high Bi-doping Ge0.64Bi0.32Fe0.04Te rather than in that with low Bi-doping concentration, indicating that the ferromagnetic establishment is entirely dependent on carrier’s transmissions. The first-principles calculation performed on this system also reveals that the ferromagnetic state exactly exists in the present n-type diluted magnetic semiconductors with Bi co-dopants.
关键词： N-type semiconductor,Ferromagnetism,Diluted magnetic semiconductors
更新于2025-09-23 15:22:29
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Ab-Initio Prediction of Intrinsic Half-Metallicity in Binary Alkali–Metal Chalcogenides: KX (X=S, Se and Te)
摘要： First-principles full-potential linearized augmented plane-wave method based on density functional theory is used to investigate the structural, electronic and magnetic properties of KX (X ? S, Se and Te) binary alkali–metal chalcogenides compounds. These compounds in different crystalline phases, NaCl (B1), CsCl (B2), ZB (B3), NiAs (B81T, WZ (B4) and Pnma, were calculated within the generalized gradient approximation (GGA-PBE) and the modified Becke–Johnson approach (mBJ-GGA-PBE) for the exchange–correlation energy and potential. We found that the most stable phase for the KX binary compounds is the nonmagnetic Pnma phase. The calculated lattice parameters, bulk moduli, their first-pressure derivatives and internal parameters are in good agreement with the other theoretical data. The electronic band structure and density of states show that half-metallic and magnetic character arises, which can be attributed to the presence of spin-polarized p orbitals in the group VI elements. KX (X ? S, Se and Te) compounds, except for KSe and KTe in the CsCl and NiAs phases, show HM character in all phases, with an integer magnetic moment of 1 (cid:1)B per formula unit and HM gaps.
关键词： alkali metals,Density functional theory,half-metals,chalcogenides,ferromagnetism
更新于2025-09-23 15:22:29
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Ferromagnetic Order in Substitutional Fe-doped In2O3 Powder
摘要： We report an experimental investigation of the room-temperature ferromagnetism of an Fe-doped In2O3 system. (In1?xFex)2O3(x = 0.00, 0.02, 0.06,0.10,0.14 or 0.18) powders were prepared by a standard solid-state reaction method followed by sintering in air at 1200 °C for 48h. The influence of Fe-doping concentration on the structural and magnetic properties of the In2O3 samples was studied. X-ray diffraction analysis reveals that Fe ions are incorporated into the In3+ sites of the In2O3 lattice without altering the cubic bixbyite structure. Magnetic characterization shows ferromagnetic behavior at room temperature for all the Fe-doped In2O3 samples. The observed ferromagnetism is attributed to the oxygen vacancies induced by substitution of Fe into In3+ sites and vacuum annealing. A model of ferromagnetic exchange interactions was proposed to explain the ferromagnetism in this system.
关键词： DMS,RTFM,Fe doped In2O3,Defects,Ferromagnetism
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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Lighta??Controlled Ferromagnetism in Porphyrin Functionalized Ultrathin FeS Nanosheets
摘要： The intrinsically weak photomagnetic interaction makes it difficult to realize effectively light-controlled magnetic structure transformation. Here unprecedented light-induced switching of magnetism is reported in porphyrin functionalized ultrathin FeS nanosheets. Contrary to the antiferromagnetic (AFM) bulk, the troilite FeS nanosheets demonstrate a ferromagnetic (FM) behavior due to superficial symmetry breaking. Under light irradiation, a large number of photo-generated carriers take part in a singlet-to-triplet conversion through intersystem crossing of tetra(4-carboxyphenyle)porphyrin molecules decorated on the nanosheets. The generated triplet carriers make spin flips occur at FeS surface, finally leading to a magnetic structure transition from FM to AFM configuration. The findings not only shed new light on steering arrangement of spin electrons but also open up almost unlimited possibilities for spintronics and optical detection of spin-dependent physiological reactions.
关键词： structural phase transition,spin flip,light-controlled ferromagnetism
更新于2025-09-23 15:21:01
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A Bean-Like Formation of Germanium Nanoparticles Inside CNTs by the Subsequent Operation of Colloidal Synthesis and Catalytic Chemical Vapor Deposition Methods
摘要： The first attempts of implanting Ge nanoparticles (Ge NPs) inside iron filled CNTs (IF-CNTs) by a subsequent use of the bench top colloidal synthesis and chemical vapor deposition (CVD) approach is shown. Ge NPs are colloidally synthesized (with a 3.8 ± 0.6 nm in size) before the deposition. The hybrid Ge NPs/IF-CNTs structure and morphology are characterized using high-resolution transmission electron microscopy, scanning electron microscopy, selective area electron diffraction, and X-ray diffraction studies. After the deposition, Ge NPs appear to be grown in size and to be sprinkled almost homogeneously into the IF-CNTs similar to a bean-like deposition. CNTs diameter is also identified to be enlarged drastically when using Ge NPs as a catalyst in CVD compared to the CNTs formation without Ge NPs. In addition, micro-length rectangular Ge μPs are also found outside the nanotube core. Rietveld analysis shows the presence of γ-Fe (Fm-3m), ferromagnetic α-Fe (Im-3m), Fe3C, Ge (Fd-3m), and multiwall CNTs. The results indicate that Ge NPs and IF-CNTs demonstrate cocatalytic activity in increasing the respective sizes, which are dramatically larger than those obtained by the conventional approaches.
关键词： ferromagnetism,germanium,nanoparticles,colloidal,chemical vapor deposition,CNTs
更新于2025-09-23 15:21:01
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Resistive switching and electric field control of ferromagnetism in SnO2 films deposited at room temperature
摘要： The SnO2 film deposited at room temperature (RT) on the substrate of Pt/Ti/SiO2/Si is nano-crystallized, which exhibits room temperature ferromagnetism (FM) due to the oxygen vacancies of SnO2 film. The bipolar and multilevel resistive switching (RS) can be observed in the Ta/SnO2/Pt devices, where SnO2 film was deposited at RT. The Ta/SnO2/Pt device has a large ON/OFF ratio (27000) and multilevel RS, which is of great significance for high-density data storage applications. The saturation magnetization of Ta/SnO2/Pt/Ti/SiO2/Si (Ta/SnO2/Pt device) is almost the same as SnO2/Pt/Ti/SiO2/Si, which implies that the influence of Ta top electrodes on the saturation magnetization of Ta/SnO2/Pt/Ti/SiO2/Si is much less. The Ta/SnO2/Pt device shows the non-volatile and reversible saturation magnetization modulation between low resistance state (LRS) and high resistance state (HRS), which results from the formation/rupture of oxygen vacancy filaments. The saturation magnetization at LRS is higher than that at HRS. In addition, the saturation magnetization also enhances with an increase the magnitude of positive DC sweeping voltage. Without DC loop current, the saturation magnetization of Ta/SnO2/Pt increases with an application of positive electric field and drops again with an application of certain negative electric field. The saturation magnetization of Ta/SnO2/Pt can be reversibly modulated in non-volatile by only electric voltage without DC loop current. Such modulation of Ms by only electric voltage without loop DC current is connected with the change in Vo+ density in a certain range of SnO2 films.
关键词： oxygen vacancies,electric field control,room temperature ferromagnetism,resistive switching,SnO2 film
更新于2025-09-23 15:21:01