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Room temperature multiferroic properties of Fe-doped nonstoichiometric SrTiO3 ceramics at both A and B sites
摘要： This letter reports the structural, dielectric, ferroelectric, and magnetic properties of Fe substituted nonstoichiometric STO ceramics. X-ray diffraction and Scanning electron microscope reveal the microstructure of the samples. The room temperature multiferroicity of the Fe-doped Ti-rich STO ceramics is successfully realized by M-H hysteresis loop, P-E hysteresis loop and magnetodielectric measurement. The origins of ferroelectricity may be related to the lattice distortions and antisite-like defects with net local dipoles. The ferromagnetism are mainly contributed by the competitions among the double exchange interactions, super-exchange interactions and the non-linear ferromagnetic exchange coupling. In addition, the ordered spin arrangement of the ferromagnetism is formed by the exchange interaction of Fe atom using first principle simulations.
关键词： D. Ferromagnetism,A. Perovskite,E. Solid-state reactions,D. Ferroelectricity
更新于2025-09-09 09:28:46
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Effect of Synthesis Temperature on Structural, Optical, and Magnetic Properties of ZnO Nanoparticles Synthesized by Combustion Method
摘要： ZnO nanoparticles at different temperatures were synthesized by using the combustion method. The effect of synthesis temperature on the properties of the nanoparticles was studied by using XRD, FESEM, EDS, TEM, photoluminescence (PL), Raman, diffuse reflectance spectra (DRS), and VSM characterization techniques. The XRD results reveal that the grown nanoparticles have a hexagonal wurtzite structure without any impurities and agreed with EDS results. FESEM and TEM micrographs show that the ZnO nanoparticles possess a spherical shape with agglomeration free, and the size increases with increase of synthesis temperature. From DRS studies, it was noticed that the band gap decreases with increase of synthesis temperature. In PL studies, blue peak at 465 nm may be due to defect-related transitions. A sharp intense peak in Raman spectra at 485 cm?1 represents E2H mode is a characteristic of a hexagonal wurtzite structure. The magnetic studies show that the magnetization decreases from 0.0172 to 0.0042 emu/g as the synthesis temperature increases from 400 to 550 °C. ZnO synthesized at 500 °C has a large squareness ratio. These materials are potential candidates for memory devices.
关键词： Combustion method,Spintronics,Ferromagnetism,ZnO nanoparticles
更新于2025-09-09 09:28:46
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Investigation of half-metallic ferromagnetism in hafnium and tantallum doped NiO for spintronic applications: A DFT study
摘要： Full Potential Linearised Augmented Plane Wave (FP-LAPW) method was used to investigate the electronic and magnetic properties of NiO doped with Hf and Ta within the frame work of density functional theory(DFT). NiO is found to be stable in rock salt structure. NiO shows metallic character for the lattice constant of 4.155?. Doping Hf and Ta in the metallic super cell of NiO separately in the doping concentration of 12.5%, the compounds Hf0.125Ni0.875O and Ta0.125Ni0.875O are formed. These compounds of Hf0.125Ni0.875O and Ta0.125Ni0.875O are found to be stable in the ferromagnetic phase. The density of states and band structure plots predict that these compounds exhibit half metallic character with formation of energy gap in one of the spins at the Fermi level. The total spin magnetic moments found in these compounds are 12.00689 μB and 10.97628 μ B.
关键词： DFT,Hf and Ta doping,spintronics,Half-metallic ferromagnetism,NiO
更新于2025-09-09 09:28:46
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Theoretical and Experimental Evidence of Modified Structure, Magnetism and Optical Properties in Ba and Mn Co-Substituted BiFeO <sub/>3</sub>
摘要： To improve the vacancy related defects associated with pure BiFeO3 (BFO) different Ba-Mn co-doped samples (Bi1-xBaxFeyMnyO3; x=0.1; y=0.0, 0.05, 0.1, 0.15) were prepared from sol-gel method. The influence of co-doping on structural, magnetic and optical properties of BiFeO3 has been studied in different experimental conditions. Particle size and magnetic properties were measured from SEM and VSM analysis respectively. Again band gap was calculated from UV analysis. The co-doped samples showed reduced particles size as well as better surface morphology. M-H loops suggest that the presence of Mn2+ increased ferromagnetic quantity at some levels. Still room temperature occurrence of ferromagnetism obtained from M-H loops of all samples showed weak ferromagnetic behaviour. In addition the incorporation of Ba2+ at Bi3+ site and Mn2+ at Fe3+ site decreased the band gap which was evidenced by increased optical property.
关键词： Surface morphology,Ferromagnetism,BFO,Multiferroics,Band gap
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
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A Study on the Weak Ferromagnetism of Nanocrystalline Stannous Oxide Induced by L-Shaped O-Sn-O Vacancies
摘要： Nanocrystalline stannous oxide (SnO) powder has been prepared by ball-milling of micron-SnO in a nitrogen atmosphere. A cation deficiency of 6.5% was found in the nano-SnO sample by X-ray photoelectron spectroscopy. After annealing at 350, 450, or 550℃ under dynamic vacuum conditions, oxygen vacancies were found in the nano-SnO samples, as verified by electron paramagnetic resonance experiments. The samples displayed weak ferromagnetism; that with both 6.5% Sn and at least 7.5% O vacancies showed the maximum saturation magnetization, reaching almost 1.7×10?3 emu/g at room temperature. The O vacancies tended to gather around Sn vacancies. An L-shaped defect model composed of one Sn and two O vacancies has been established, and its ferromagnetism has been calculated by a first-principles method. We found that the L-shaped defect induced a magnetic moment of 0.55 μB in the SnO lattice, the main contribution to which came from a spin-polarized electron in the p orbital of a corner Sn atom.
关键词： Magnetic,Nanocrystalline Stannous Oxide,Plasmonics,L-Shaped O-Sn-O Vacancies,Weak Ferromagnetism,Optical,Hybrid Materials
更新于2025-09-04 15:30:14