Enhanced magnetic performance in exchange coupled CoFe2O4 - LaFeO3 nanocomposites

2021 ◽  
Author(s):  
Priyanka Sharma ◽  
Anjali Jain ◽  
Ratnamala Chatterjee
Keyword(s):  
Structural Parameters ◽  
Magnetic Loss ◽  
Sol Gel ◽  
Magnetic Hysteresis ◽  
Shell Morphology ◽  
Magnetic Interactions ◽  
Core Shell ◽  
Remarkable Feature ◽  
X Ray ◽  
Magnetic Performance

Abstract Nanocomposite oxide system of (x)CoFe2O4 - (100-x)LaFeO3 with different weight percent of core-shell structured CoFe2O4 (x = 0,20,40,50,80,100) and LaFeO3 were fabricated, via a two-step sol-gel wet-chemical synthesis technique. The phase formation of the composites was confirmed by X-ray diffraction and the structural parameters of both the phases were attained from the Rietveld refinement results of XRD patterns. The elemental composition and microstructure of the resulting nanocomposites were examined by using energy-dispersive X-ray spectroscopy (EDX) and high-resolution transmission electron microscopy (HRTEM) technique, respectively. The detailed magnetometry studies at 300 K and 5 K reveal that the inter-and intra-phase magnetic interactions affect the saturation magnetization (MS), remanence magnetization (MR) and coercivity (HC) values of this bi-magnetic system. The remarkable feature of “pinched magnetic hysteresis loop” was evidenced in the [(50) CoFe2O4 - (50)LaFeO3] composite, leading to a lesser magnetic loss factor and better magnetic performance of this sample. The report depicts an improved interfacial exchange coupling at 5 K, for the nanocomposites of core-shell morphology and offers an understanding or explanation of improved magnetic performance for the (50)CoFe2O4 - (50)LaFeO3 nanocomposite and opens up an important way to design new multiferroic applications in low magnetic fields.

scholarly journals Lead-Free BNT–BT0.08/CoFe2O4 Core–Shell Nanostructures with Potential Multifunctional Applications

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 672
Author(s):  
Marin Cernea ◽  
Roxana Radu ◽  
Harvey Amorín ◽  
Simona Gabriela Greculeasa ◽  
Bogdan Stefan Vasile ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Molar Ratio ◽  
Transmission Electron Microscopy Data ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Two Phase ◽  
X Ray ◽  
Shell Nanostructures

Herein we report on novel multiferroic core–shell nanostructures of cobalt ferrite (CoFe2O4)–bismuth, sodium titanate doped with barium titanate (BNT–BT0.08), prepared by a two–step wet chemical procedure, using the sol–gel technique. The fraction of CoFe2O4 was varied from 1:0.5 to 1:1.5 = BNT–BT0.08/CoFe2O4 (molar ratio). X–ray diffraction confirmed the presence of both the spinel CoFe2O4 and the perovskite Bi0.5Na0.5TiO3 phases. Scanning electron microscopy analysis indicated that the diameter of the core–shell nanoparticles was between 15 and 40 nm. Transmission electron microscopy data showed two–phase composite nanostructures consisting of a BNT–BT0.08 core surrounded by a CoFe2O4 shell with an average thickness of 4–7 nm. Cole-Cole plots reveal the presence of grains and grain boundary effects in the BNT–BT0.08/CoFe2O4 composite. Moreover, the values of the dc conductivity were found to increase with the amount of CoFe2O4 semiconductive phase. Both X-ray photoelectron spectroscopy (XPS) and Mössbauer measurements have shown no change in the valence of the Fe3+, Co2+, Bi3+ and Ti4+ cations. This study provides a detailed insight into the magnetoelectric coupling of the multiferroic BNT–BT0.08/CoFe2O4 core–shell composite potentially suitable for magnetoelectric applications.

Synthesis and Characterization of SiO2@Y2MoO6:Eu3+ Core–Shell Structured Spherical Phosphors by Sol–Gel Process

2016 ◽  
Vol 16 (4) ◽  
pp. 3914-3920 ◽  
Author(s):  
G. Z Li ◽  
F. H Liu ◽  
Z. S Chu ◽  
D. M Wu ◽  
L. B Yang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Annealing Temperature ◽  
Uv Light ◽  
Sol Gel ◽  
Spherical Shape ◽  
Core Shell ◽  
X Ray ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Average Size

SiO2@Y2MoO6:Eu3+ core–shell phosphors were prepared by the sol–gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as kinetic decays were used to characterize the resulting SiO2@Y2MoO6:Eu3+ core–shell phosphors. The XRD results demonstrated that the Y2MoO6:Eu3+ layers on the SiO2 spheres crystallized after being annealed at 700 °C and the crystallinity increased with raising the annealing temperature. The obtained core–shell phosphors have spherical shape with narrow size distribution (average size ca. 640 nm), non-agglomeration, and smooth surface. The thickness of the Y2MoO6:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (70 nm for four deposition cycles). The Eu3+ shows a strong PL emission (dominated by 5D0–7F2 red emission at 614 nm) under the excitation of 347 nm UV light. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles.

X-ray absorption spectroscopy studies of phase transformations and amorphicity in nanotitania powder and silica–titania core–shell photocatalysts

2008 ◽  
Vol 41 (6) ◽  
pp. 1009-1018 ◽  
Author(s):  
S. H. Lim ◽  
N. Phonthammachai ◽  
T. Liu ◽  
T. J. White
Keyword(s):  
Absorption Spectroscopy ◽  
Sol Gel ◽  
Local Environment ◽  
Core Shell ◽  
Transformation Mechanism ◽  
X Ray ◽  
Amorphous Content ◽  
Silica Substrate ◽  
The Core ◽  
X Ray Absorption

The local environment of titanium in nanocrystalline sol-gel synthesized titania, cobaltiferous titania and silica–titania core–shell photocatalysts was investigated using X-ray absorption spectroscopy (XAS). Anatase reconstructively transforms to rutileviaa persistent amorphous phase that is retained, in part, up to 1273 K. In nanotitania, temperature-dependent trends in Ti order correlation observed by XAS parallel the development of amorphous content extracted from powder X-ray diffraction patterns, such that amorphicity shows a transient maximum at ∼873 K with the onset of rutile crystallization. Cobaltiferous and core–shell materials behaved similarly, but with anatase retained to 973 and 1273 K, respectively. In the former, cobalt redox reactions may stabilize anatase to higher temperatures by ready charge-balancing during the loss of hydroxyl and the formation of oxygen vacancies. In the core–shell architecture, higher Ti coordination and interatomic distance variance in the first- and second-nearest-neighbour shells are maintained to 1273 K by interaction of a substantially aperiodic TiO6network with the glassy silica substrate, which inhibits crystallization of rutile from the amorphous intermediate. Comparisons are also drawn with the commercial P25 catalyst. The overall transformation mechanism can be summarized as gel → non-stoichiometric anatase → amorphous titania → rutile. Smaller anatase crystals and a higher average Ti—Ti coordination environment in the core–shell structure may enhance photocatalytic activity directly, by creating larger specific surface areas and hosting reactive defects, or indirectly, by inhibiting exciton annihilation in aperiodic titania and delaying the crystallization of less photoactive rutile.

Structural and Magnetic Properties of CoFe2O4 / Si (001) Thin Films via Sol-Gel Method

2013 ◽  
Vol 744 ◽  
pp. 315-318
Author(s):  
Wei Rao ◽  
Ding Guo Li ◽  
Hong Chun Yan
Keyword(s):  
Thin Films ◽  
Magnetic Properties ◽  
Exchange Coupling ◽  
Cobalt Ferrite ◽  
Sol Gel ◽  
Magnetic Hysteresis ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Calcined Temperature

Cobalt ferrite (CoFe2O4) thin films have been prepared on Si (001) substrates, with different calcined temperatures (Tcal=400°C~800°C). The films structure was studied by X-ray diffraction (XRD) and their surface was examined by scanning electron microscopy (SEM). The magnetic properties were measured with a vibrating sample magnetometer (VSM). For low calcined temperatures, the films presented a mixture of a CoFe2O4phase, with the cubic spinel structure, and cobalt and iron antiferromagnet oxides with CoO and FeO stoichiometries. As the calcined temperature increased, the CoO and FeO relative content strongly decreased, so that for Tcal=800°Cthe films were composed mainly by polycrystalline CoFe2O4. The magnetic hysteresis cycles measured in the films were horizontally shifted due to an exchange coupling field originated by the presence of the antiferromagnetic phases.

Comparative Study on Mn-Zn Ferrites by One-Step Synthesis and Conventional Two-Step Synthesis

2010 ◽  
Vol 177 ◽  
pp. 260-263 ◽  
Author(s):  
Qing Kai Xing ◽  
Zhi Jian Peng ◽  
Xiu Li Fu ◽  
Zhi Qiang Fu ◽  
Cheng Biao Wang ◽  
...  
Keyword(s):  
Magnetic Hysteresis ◽  
Initial Permeability ◽  
Synthesis Methods ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Magnetic Performance ◽  
One Step ◽  
The Difference ◽  
The One

Mn-Zn ferrites doped with Cr3+ were prepared by “one-step synthesis” and conventional two-step synthesis methods, respectively. Their phase compositions and microstructures were characterized by X-ray diffraction and scanning electron microscopy, respectively. And their magnetic magnetic performance, such as saturation magnetization (Ms), magnetic hysteresis, initial permeability μi and power loss were comparatively investigated by vibrating sample magnetometer. It was observed that the difference of magnetic performance of the samples prepared by both methods is little. The similar performance of both methods makes the “one-step synthesis” especially attractive for application when considering energy economization.

Synthesis and Luminescent Properties of Monodisperse Spherical SiO2/Ca10(PO4)6(OH)2: Eu3+ Particles with Core-Shell Structure

2014 ◽  
Vol 1004-1005 ◽  
pp. 344-347
Author(s):  
Huan Wang
Keyword(s):  
Smooth Surface ◽  
Calcium Phosphates ◽  
Sol Gel ◽  
Spherical Shape ◽  
Luminescent Properties ◽  
Core Shell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sol Gel Process ◽  
Shell Particles

The growing necessity of biomaterials has increased the interest in calcium phosphates, particularly hydroxyapatite. In this paper, monodisperse and spherical SiO2particles have been coated with Ca10(PO4)6(OH)2:Eu3+layers via a Pechini sol-gel process, resulting in core-chell ctructured SiO2/Ca10(PO4)6(OH)2:Eu3+samples. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL) spectra were employed to characterize the SiO2/Ca10(PO4)6(OH)2:Eu3+core-shell particles. The resulted core-shell particles have perfect spherical shape with narrow size distribution, smooth surface and non-agglomeration.

Nonsurfactant Surface Modifications of Monodispersed Si-Cu Core-Shell Nanocomposite

2014 ◽  
Vol 895 ◽  
pp. 571-574
Author(s):  
Musdalilah Ahmad Salim ◽  
Halina Misran ◽  
S.Z. Othman ◽  
N.N.H. Shah ◽  
N.A.A. Razak ◽  
...  
Keyword(s):  
Sol Gel ◽  
Core Shell ◽  
Silica Spheres ◽  
X Ray Diffraction ◽  
Stöber Method ◽  
X Ray ◽  
Silica Surfaces ◽  
Nonsurfactant Template ◽  
Diffraction Patterns ◽  
Modified Stöber Method

Monodispersed silica spheres with particles size of ca. 450 nm were successfully synthesized using modified Stöber method. The synthesized monodispersed silica spheres were successfully coated with copper through modified sol-gel method employing nonsurfactant template and catalyst. A renewable nonsurfactant template, decyl-alcohol (C10) and catalyst were used to modify the silica surfaces prior to coating with copper. In order to study the effect of catalyst on copper deposition onto silica surfaces, ammonia was used as catalyst in various amounts. The X-ray diffraction patterns of Si-Cu core-shell exhibited a broad peak corresponding to amorphous silica networks and exhibited monoclinic CuO phase. It was found that samples modified in the presence of 1 ml catalyst exhibited relatively homogeneous deposition. The surface area of uncoated core (SiO2) was at ca. 7.04 m2/g and coated samples 1 ml catalyst was at ca. 8.21m2/g.

Small-angle x-ray analysis of latex particles with core-shell morphology

1993 ◽  
Vol 271 (6) ◽  
pp. 563-572 ◽  
Author(s):  
R. Grunder ◽  
G. Urban ◽  
M. Ballauff
Keyword(s):  
Small Angle ◽  
Shell Morphology ◽  
Core Shell ◽  
Latex Particles ◽  
X Ray

Complete structural and strain analysis of single GaAs/(In,Ga)As/GaAs core–shell–shell nanowires by means of in-plane and out-of-plane X-ray nanodiffraction

2018 ◽  
Vol 51 (5) ◽  
pp. 1387-1395 ◽  
Author(s):  
Ali Al Hassan ◽  
Arman Davtyan ◽  
Hanno Küpers ◽  
Ryan B. Lewis ◽  
Danial Bahrami ◽  
...  
Keyword(s):  
Shell Thickness ◽  
Lattice Mismatch ◽  
Bragg Reflection ◽  
Structural Parameters ◽  
Core Shell ◽  
X Ray ◽  
Growth Axis ◽  
The Core ◽  
Out Of Plane ◽  
Interface Strain

Typically, core–shell–shell semiconductor nanowires (NWs) made from III–V materials with low lattice mismatch grow pseudomorphically along the growth axis, i.e. the axial lattice parameters of the core and shell materials are the same. Therefore, both the structural composition and interface strain of the NWs are encoded along directions perpendicular to the growth axis. Owing to fluctuations in the supplied growth species during molecular beam epitaxy (MBE) growth, structural parameters such as local shell thickness, composition and strain may differ between NWs grown onto the same substrate. This requires structural analysis of single NWs instead of measuring NW ensembles. In this work, the complete structure of single GaAs/(In,Ga)As/GaAs core–shell–shell NW heterostructures is determined by means of X-ray nanodiffraction using synchrotron radiation. The NWs were grown by MBE on a prepatterned silicon (111) substrate with a core diameter of 50 nm and an (In,Ga)As shell thickness of 20 nm with a nominal indium concentration of 15%, capped by a 30 nm GaAs outer shell. In order to access single NWs with the X-ray nanobeam being incident parallel to the surface of the substrate, a single row of holes with a separation of 10 µm was defined by electron-beam lithography to act as nucleation centres for MBE NW growth. These well separated NWs were probed sequentially by X-ray nanodiffraction, recording three-dimensional reciprocal-space maps of Bragg reflections with scattering vectors parallel (out-of-plane) and perpendicular (in-plane) to the NW growth axis. From the out-of-plane 111 Bragg reflection, deviations from hexagonal symmetry were derived, together with the diameters of probed NWs grown under the same conditions. The radial NW composition and interface strain became accessible when measuring the two-dimensional scattering intensity distributions of the in-plane 2{\overline 2}0 and 22{\overline 4} reflections, exhibiting well pronounced thickness fringes perpendicular to the NW side planes (truncation rods, TRs). Quantitative values of thickness, composition and strain acting on the (In,Ga)As and GaAs shells were obtained via finite-element modelling of the core–shell–shell NWs and subsequent Fourier transform, simulating the TRs measured along the three different directions of the hexagonally shaped NWs simultaneously. Considering the experimental constraints of the current experiment, thicknesses and In content have been evaluated with uncertainties of ±2 nm and ±0.01, respectively. Comparing data taken from different single NWs, the shell thicknesses differ from one to another.

Preparation and Electromagnetic Wave Absorption Properties of Core-Shell Ni/TiO2 Microspheres

2014 ◽  
Vol 602-603 ◽  
pp. 762-766
Author(s):  
Biao Zhao ◽  
Bing Bing Fan ◽  
Hao Chen ◽  
Xiao Xuan Pian ◽  
Bin Bin Wang ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Microwave Absorption ◽  
Magnetic Loss ◽  
Core Shell ◽  
Absorption Properties ◽  
Microwave Absorption Properties ◽  
Electromagnetic Wave Absorption ◽  
X Ray ◽  
Wave Absorption ◽  
Chloride Hexahydrate

The composite microspheres with Ni cores and amorphous TiO2 shells (Ni@TiO2) were synthesized by a one-pot solvothermal method at 180°C for 15 h, which used nickel chloride hexahydrate as Ni source andtetrabutyl orthotitanate as Ti source. The Ni/TiO2 core/shell composites were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX). A possible formation mechanism of core-shell Ni/TiO2 was proposed. Furthermore, the microwave absorption properties of these microspheres were investigated in terms of complex permittivity and permeability. The minimum reflection loss is-29.5 dB at 14.4 GHz for a layer of 4.0 mm thickness. Such phenomenon is attributed to the synergy effect between magnetic loss of Ni core and dielectric loss of amorphous TiO2 shell. The enhanced microwave absorption properties are also believed to be due to the unique coreshell structure. All results indicate that these Ni@TiO2 microspheres may be attractive candidate materials for electromagnetic wave absorption applications.

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