Magnetic Properties of Ni Nanoparticles Embedded in Amorphous SiO2

2002 ◽  
Vol 746 ◽  
Author(s):  
Fabio C. Fonseca ◽  
Gerardo F. Goya ◽  
Renato F. Jardim ◽  
Reginaldo Muccillo ◽  
Neftalí L. V. Carreño ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Temperature Dependence ◽  
Excellent Agreement ◽  
Magnetic Moments ◽  
Magnetic Hysteresis ◽  
Blocking Temperature ◽  
Spherical Particles ◽  
Average Particle ◽  
Ni Nanoparticles ◽  
Tem Analysis

ABSTRACTA modified sol-gel technique was used to synthesize nanocomposites of Ni:SiO2 which resulted in Ni nanoparticles embedded in a SiO2 amorphous matrix. Transmission electron microscopy TEM analysis were performed to study the structure and morphology of the magnetic powders. The Ni particles were found to have a good dispersion and a controlled particle size distribution, with average particle radius of ∼ 3 nm. A detailed characterization of the magnetic properties was done through magnetization measurements M(T,H) in applied magnetic fields up to ± 7 T and for temperatures ranging from 2 to 300 K. The superparamagnetic (SPM) behavior of these metallic nanoparticles was inferred from the temperature dependence of the magnetization. The blocking temperature TB, as low as 20 K, was found to be dependent on Ni concentration, increasing with increasing Ni content. The SPM behavior above the blocking temperature TB was confirmed by the collapse of M/MS vs. H/T data in universal curves. These curves were fitted to a log-normal weighted Langevin function allowing us to determine the distribution of magnetic moments. Using the fitted magnetic moments and the Ni saturation magnetization, the radii of spherical particles were determined to be close to ∼ 3 nm, in excellent agreement with TEM analysis. Also, magnetic hysteresis loops were found to be symmetric along the field axis with no shift via exchange bias, suggesting that Ni particles are free from an oxide layer. In addition, for the most diluted samples, the magnetic behavior of these Ni nanoparticles is in excellent agreement with the predictions of randomly oriented and noninteracting magnetic particles. This was confirmed by the temperature dependence of the coercivity field that obeys the relation HC(T) = HC0 [1-(T/TB)1/2] below TB with HC0 ∼ 780 Oe.

MAGNETIC PROPERTIES OF Ni NANOPARTICLES

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4390-4394 ◽  
Author(s):  
Y. T. JEON ◽  
J. Y. MOON ◽  
G. H. LEE ◽  
J. PARK
Keyword(s):  
Magnetic Properties ◽  
Saturation Magnetization ◽  
Magnetic Moments ◽  
Particle Diameter ◽  
Average Particle ◽  
Ni Nanoparticles ◽  
Size Dependent

We investigated the size dependent magnetic properties of Ni nanoparticles. We prepared four samples with average particle diameters of 7.0, 14.0, 16.5, and 20.0 nm. The blocking temperatures (TBs) were 40.0, 150.0, 250.0, and ~ 300.0 K for the above Ni nanoparticles, respectively. Saturation magnetization increased with increasing particle diameter due to the reduced magnetic moments of surface atoms. The coercivities at 5 K ranged from 270 and 340 Oe, whereas those at 300 K were zero due to superparamagnetism.

Processing and Properties of Nanostructured Magnetic Materials

2002 ◽  
Author(s):  
D. Kumar ◽  
S. Yarmolenko ◽  
J. Sankar ◽  
J. Narayan ◽  
A. Tiwari ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Hysteresis ◽  
Single Domain ◽  
Dead Layer ◽  
Blocking Temperature ◽  
Ferromagnetic Behavior ◽  
Ni Nanoparticles ◽  
Interface Control ◽  
Individual Grains ◽  
Oxygen Bond

We report here a novel thin film processing method based upon pulsed laser deposition to process nanocrystalline materials with accurate size and interface control with improved mechanical and magnetic properties. Using this method, single domain nanocrystalline Fe and Ni particles in 5–10 nm size range embedded in amorphous alumina as well as crystalline TiN have been produced. By controlling the size distribution in confined layers, it was possible to tune the magnetic properties from superparamagnetic to ferromagnetic behavior. Magnetic hysteresis characteristics below the blocking temperature are consistent with single-domain behavior. The paper also presents our results from investigations in which scanning transmission electron microscopy with atomic number contrast (STEM-Z) and energy loss spectroscopy (EELS) were used to understand the atomic structure of Ni nanoparticles and interface between the nanoparticles and the surrounding matrices. It was interesting to learn from EELS measurements at interfaces of individual grains that Ni in alumina matrix does not from an ionic bond indicating the absence of metal-oxygen bond at the interface. The absence of metal-oxygen bond, in turn, suggests the absence of any dead layer on Ni nanoparticles even in an oxide matrix.

Tunable Magnetic and Mechanical Properties in Metal Ceramic Composite Thin Films

2001 ◽  
Author(s):  
D. Kumar ◽  
J. Sankar ◽  
J. Narayan ◽  
A. Kvit
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Magnetic Properties ◽  
Smart Materials ◽  
Quantum Interference ◽  
Composite Structures ◽  
Magnetic Hysteresis ◽  
Single Domain ◽  
Blocking Temperature ◽  
Research Activities

Abstract Presently a wide spread of research activities is pursued in the area of theoretical, computational and experimental aspects of vibration studies in laminated composite structures with embedded or surface bonded smart layers in order to improve the performance of components in aerospace, mechanical, robotics, and electronic equipments. The key to the successful fabrication of these components with improved properties is the development of smart materials by materials engineering and understanding the fundamentals of materials science. It is in this context that we have developed a novel smart thin film processing method based upon pulsed laser deposition to process nanocrystalline materials with accurate size and interface control with improved mechanical and magnetic properties. Using this method, single domain nanocrystalline Fe and Ni particles in 5–10 nm size range embedded in amorphous as well as crystalline alumina have been produced. By controlling the size distribution in confined layers, it was possible to tune the magnetic properties from superparamagnetic to ferromagnetic in a controlled way. Magnetization measurements of these thin film composites as function of field and temperature were carried out using a superconducting quantum interference device (SQUID) magnetometer. Magnetic hysteresis characteristics below the blocking temperature are consistent with single-domain behavior. Mechanical properties were measured using nano-indentation measurements. The hardness of the Fe and Ni-Al2O3 nanocomposites was found to vary strongly with the size do Fe and Ni nanodots in the alumina matrix. For example, the hardness of Fe-Al2O3 system increased from 15 GPa to 28 GPa when the size of Fe dots in alumina was increased from 5 nm to 9 nm. It is envisioned that this types of smart films can be used in magnetic recording, ferrofluid technology, magnetocaloric refrigeration, biomedicine, biotechnology, aerospace applications where hard and wear-resistant coatings are also very important for its survival.

Nickel Nanocomposite Thin Films

2001 ◽  
Vol 703 ◽  
Author(s):  
Honghui Zhou ◽  
A. Kvit ◽  
D. Kumar ◽  
J. Narayan
Keyword(s):  
Quantum Interference ◽  
Magnetic Measurements ◽  
Magnetic Moments ◽  
Deposition Process ◽  
Blocking Temperature ◽  
Ni Nanoparticles ◽  
Epitaxial Relationship ◽  
Transmission Electron ◽  
Nanocomposite Thin Films ◽  
Matrix Layer

ABSTRACTNickel was deposited on epitaxial TiN matrix layer grown on Si (100) substrate by pulsed laser deposition process (PLD). Transmission electron microscopy (TEM) study shows that nanoparticles formed are single crystals with two kinds of epitaxial relationship with respect to matrix TiN. One is cube on cube, where (200) Ni // (200) TiN // (200) Si and (022) Ni // (022) TiN // (022) Si. The particles grown in this orientation have a trapezoidal morphology in [011] projection. The other involves a 90 ° rotation with respect to [011] direction of TiN matrix (zone axis), where (022) Ni // (200) TiN // (200) Si and (200) Ni // (022) TiN // (022) Si. The particles grown in this rotated orientation have a triangular morphology in [011] projection and a smaller lattice constant compared with that of pure nickel. The possible mechanism of forming these two epitaxial orientations is discussed. Superconducting quantum interference device (SQUID) magnetometer was used for magnetic measurements. In order to investigate the effect of texturing on magnetic properties of nanoparticles, results were compared with those obtained from Ni nanoparticles grown on amorphous Al2O3 matrix layer in previous research. It was found that both blocking temperature and coercivity of Ni nanoparticles grown on epitaxial TiN matrix are significantly higher than that of Ni grown on amorphous Al2O3. The higher value of coercivity is possibly associated with the stronger tendency of crystallographically oriented particles to retain their magnetic moments in the presence of reversing magnetic field.

scholarly journals Structural, electronic, and magnetic properties of Ni nanoparticles supported on the TiC(001) surface

2020 ◽  
Vol 22 (45) ◽  
pp. 26145-26154
Author(s):  
Pablo Lozano-Reis ◽  
Ramón Sayós ◽  
José A. Rodriguez ◽  
Francesc Illas
Keyword(s):  
Magnetic Properties ◽  
Magnetic Moments ◽  
Ni Nanoparticles ◽  
Electronic And Magnetic Properties ◽  
Ni Clusters

Ni clusters adsorb on TiC with a quenching in their magnetic moments.

Microstructural and Magnetic Properties on Graphitic Encapsulated Ni Nanocrystals and Pure Ni Nanoparticles with NiO Layer

1999 ◽  
Vol 581 ◽  
Author(s):  
Xiangcheng Suns ◽  
M. Jose Yacamana ◽  
F. Morales
Keyword(s):  
Magnetic Properties ◽  
Room Temperature ◽  
Nickel Nanoparticles ◽  
Blocking Temperature ◽  
Morphological Properties ◽  
Zero Field ◽  
Ni Nanoparticles ◽  
Ferromagnetic Interaction ◽  
Zero Field Cooling ◽  
Field Cooling

ABSTRACTTwo kinds of different nickel nanoparticles with distinct morphological properties, Ni(C) and Ni(O), are studied. Magnetization measurements for the assembly of two kinds of Ni nanoparticles show, a larger coercivity and remanence as well as the deviation between the zero field cooling (ZFC) and the field cooling (FC) magnetization have been observed in the Ni(O) particles. This deviation may be explained as a typical cluster glass-like behavior due to ferromagnetic interaction among the assembly of Ni(O) particles. However, Ni(C) particles exhibit superparamagnetism at room temperature. The average blocking temperature (TB) is determined to around 115K. We also observe gradual decrease in saturation magnetization, which is attributed to the nanocrystalline nature of the encapsulated particles.

scholarly journals Morphology and magnetic properties of lanthanum (La3+) substituted manganese, chromium nano ferrites

2019 ◽  
Vol 10 (2) ◽  
pp. 1102
Author(s):  
Hayder Abdulameer Abbas ◽  
Adnan Hussein Ali ◽  
Ban Mohammad Hasan
Keyword(s):  
Electron Microscopy ◽  
Magnetic Properties ◽  
Sol Gel ◽  
Particle Diameter ◽  
Average Crystallite Size ◽  
Spherical Particles ◽  
Average Particle ◽  
Absorption Bands ◽  
X Ray ◽  
Manganese Chromium

<span>Several studies have been carried out to investigate the effect of Lanthanum (La<sup>3+</sup>) ion substitution on the structural and magnetic properties of manganese-chromium (Mn-Cr) ferrite of chemical formula Mn La<sub>x</sub>Cr Fe<sub>2</sub>O<sub>4</sub>(x=0.0, 0.25 and 0.5). Such studies have made efforts to improve the magnetic and structural properties of manganese-chromium (Mn-Cr) ferrite by using lanthanum substituted nano ferrites and then synthesized using the sol-gel method and annealed at a temperature of 700<sup>o</sup>C. The changes that occurred in the structure of the nano ferrites as a result of lanthanum substitution were identified using X-ray diffraction (XRD). Based on Debye-Scherrer equation, the XRD data were used in measuring the particle sizes of different diffraction and average crystallite size by means of Fourier Transform infrared spectroscopy (FTIR). In analyzing the morphology of the nano ferrites, scanning electron microscopy (SEM) was used, elemental compassion was studied using energy dispersive X-ray spectroscopy (EDAX), and the average particle diameter was determined using Transmission electron microscopy (TEM) studies. FTIR spectral analysis of the prepared samples under investigations revealed the formation of a single phase spherical particles. Two important absorption bands were observed; one (<em>ν<sub>1</sub></em>) around 556 cm<sup>-1</sup>, which is attributed to the intrinsic vibrations of tetrahedral complexes, while the other low frequency band (<em>ν<sub>2</sub></em>) was around 430 cm<sup>-1</sup>, and attributed to octahedral complexes.</span>

scholarly journals Magnetic properties of iron oxide nanoparticles with a DMSA-modified surface

2021 ◽  
Vol 242 (1) ◽  
Author(s):  
K. Winiarczyk ◽  
W. Gac ◽  
M. Góral-Kowalczyk ◽  
Z. Surowiec
Keyword(s):  
Magnetic Properties ◽  
Magnetite Nanoparticles ◽  
Magnetic Hysteresis ◽  
Blocking Temperature ◽  
Synthesis Process ◽  
Physical Parameters ◽  
Zero Field ◽  
Powder Samples ◽  
Surface Modified ◽  
Field Cooling

AbstractThe magnetic properties of magnetite nanoparticles (Fe3O4 NPs) strongly depend on their chemical and physical parameters, which can be regulated by a controlled synthesis process. To improve the quality of the obtained nanoparticles, their surface is often modified with organic compounds (from the group of surfactants, sugars, proteins, or organic acid). In this study, we synthesized magnetite nanoparticles with a surface modified with the organic compound DMSA. Then, the nanocrystallites were characterized in terms of structure and morphology. To investigate the role of DMSA and to understand the adsorption mechanism, FTIR measurements were carried out. Using Mössbauer spectroscopy, we investigated temperature-induced changes in the magnetic properties of prepared samples. The spectra were recorded in a wide temperature range (from 4 K to 390 K) for two types of samples: powders and ferrofluids with various concentrations. In the case of powder samples, the superparamagnetic doublet appeared at room temperature. For magnetic suspensions, the spectra were more complicated. They consisted of superposition of asymmetrically broadened sextets and doublets, which was caused by the occurrence of long-range dipole-dipole interactions. These interactions affected the magnetic properties of the material and increased the blocking temperature. Additionally, the magnetic hysteresis and zero field cooling-field cooling (ZFC/FC) curves were measured with the use of a vibrating sample magnetometer.

Magnetic properties of rare earth chromium borates at high temperatures

2021 ◽  
pp. 166-170
Author(s):  
O.K. Kuvandikov ◽  
◽  
N.I. Leonyuk ◽  
V.V. Malsev ◽  
M.M. Kuzmin ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Susceptibility ◽  
Rare Earth ◽  
Temperature Dependence ◽  
High Temperatures ◽  
Wide Temperature Range ◽  
Magnetic Moments ◽  
Chemical Formula ◽  
Temperature Range ◽  
Curie Temperatures

Temperature dependence of the magnetic susceptibility has been studied for rare-earth borates NdCr3(BO3)4, SmCr3(BO3)4 and LuCr3(BO3)4 by the Faradey method in the wide temperature range (300-1200 K). The dependence for each phase follows the Curi - Weis law. The Curie temperatures, Neel temperatures and magnetic moments corresponding to the chemical formula of the crystals, have been found.

Superparamagnetism and Microstructural Properties of Carbon Encapsulated Ni nanoparticle Assemblies

2001 ◽  
Vol 676 ◽  
Author(s):  
Xiang-Cheng Sun ◽  
Xinglong Dong ◽  
J. A. Toledo ◽  
M. J. Yacaman
Keyword(s):  
Arc Discharge ◽  
Spherical Shape ◽  
Good Evidence ◽  
Particle Radius ◽  
Blocking Temperature ◽  
Average Particle ◽  
Ni Nanoparticles ◽  
Microstructural Properties ◽  
Superparamagnetic Relaxation ◽  
Average Particle Radius

ABSTRACTCarbon encapsulated Ni nanoparticles (Ni(C)) were synthesized by modified arc-discharge reactor under methane atmosphere. The presence of carbon encapsulation is confirmed by HR-TEM imaging, and Nano-diffraction. The average particle radius is typically 10.5 nm with spherical shape. The intimate and contiguous carbon fringe around these Ni nanoparticles is good evidence for complete encapsulation by carbon shell layers.Superparamagnetic property studies were performed using SQUID magnetometer for the assemblies of Ni(C) nanoparticles. The blocking temperature (TB) is determined to around 115K at 1000Oe applied field. Above TB, the magnetization M (H, T) can be described by the classical Langevin function L using the relation, M/Ms(T=0) = coth(μH/kT)- kT/μH. The particle radius can be inferred from Langevin fit (particle moment μ) and blocking temperature theory (TB), which values are a little bigger than HR-TEM observations. It is suggested, these assemblies of carbon encapsulated Ni nanoparticles have been showed typical single-domain, field-dependent superparamagnetic relaxation properties.

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