Temperature-Dependent Magnetic Properties of SiO2-Coated Ni75Fe25 Nanoparticles

2002 ◽  
Vol 755 ◽  
Author(s):  
Mingzhong Wu ◽  
Y.D. Zhang ◽  
S. Hui ◽  
Shihui Ge
Keyword(s):  
Magnetic Properties ◽  
Calcination Temperature ◽  
Quantum Interference ◽  
Amorphous State ◽  
Ferromagnetic State ◽  
Oxide Content ◽  
Temperature Dependent ◽  
Bloch Constant ◽  
Transmission Electron ◽  
Increasing Temperature

ABSTRACTSiO2-coated Ni75Fe25 nanoparticles were prepared using a wet chemical method and their structure and magnetic properties were investigated using x-ray diffraction, high-resolution transmission electron microscopy, and a superconducting quantum interference device magnetometer. The SiO2 material was in an amorphous state. The Ni75Fe25 nanoparticles were in a simple cubic state and contained inner oxide (Ni-oxide and Fe-oxide) cores whose size decreased with increasing calcination temperature. The nanoparticles were basically in the ferromagnetic state. Their saturation magnetization increased with increasing calcination temperature, whereas their coercivity decreased with increasing calcination temperature. The nanoparticles exhibited strong temperature-dependent magnetic behaviors. The Bloch exponent fell from 1.5 for the bulk to smaller values and decreased with increasing oxide content, while the Bloch constant was much bigger than that for bulk and increased significantly with oxide content. The value of coercivity decreased with increasing temperature, and this decrease was more pronounced for the nanoparticles containing high oxide content. The exchange anisotropy arising from the exchange coupling across the Ni75Fe25/oxide interfaces was examined and was used to interpret the observed temperature-dependent behaviors.

Influences of the Adding Manners of b on the Stability and the Soft Magnetic Properties of Amorphous Fe52Co34Hf7B6Cu1 Alloys

2013 ◽  
Vol 320 ◽  
pp. 83-87 ◽  
Author(s):  
Yue Gu ◽  
Yue Sheng Chao
Keyword(s):  
Activation Energy ◽  
Magnetic Properties ◽  
Amorphous State ◽  
Soft Magnetic Property ◽  
Soft Magnetic Properties ◽  
Soft Magnetic ◽  
Transmission Electron ◽  
The Matrix ◽  
Quenching Method ◽  
The Stability

The stability and the soft magnetic properties of amorphous Fe52Co34Hf7B6Cu1 alloys have been investigated in this paper. Amorphous Fe52Co34Hf7B6Cu1 alloys ribbons are prepared by single-roller-quenching method. The differential thermal analysis (DTA), X-ray diffraction (XRD), Mössbauer Spectroscopy, transmission electron microscope (TEM) and vibrating sample magnetometer (VSM) were used for characterizing microstructures, soft magnetic properties, and evaluating the influence of adding manners of B on the stability of as-quenched specimens. The XRD curve shows a wide dispersion of peak, the TEM diffraction ring was dispersed cyclic, the pattern of the matrix was homogeneous, and the Mössbauer spectrum of as-quenched alloy presents a typical broadened and overlapped sextet, which confirms the as-quenched alloy in fully amorphous state. The DTA results showed the activation energy of Fe52Co34Hf7B6Cu1 alloy is 299.7KJ/mol. When pure B is replaced by FeB in preparing amorphous Fe52Co34Hf7B6Cu1 alloys, the activation energy reduced to 293.3 KJ/mol,and the soft magnetic property is decline according VSM results.

Relationship between Microstructure and Magnetic Properties of Nano-Scale Particles Formed in Cu-Ni-(FeCo) Alloys

2018 ◽  
Vol 941 ◽  
pp. 1324-1329 ◽  
Author(s):  
Shintaro Matai ◽  
Hibiki Sakakura ◽  
Mahoto Takeda
Keyword(s):  
Magnetic Properties ◽  
Quantum Interference ◽  
Magnetic Particles ◽  
Superconducting Quantum Interference Device ◽  
Recording Technology ◽  
Treatment Conditions ◽  
Transmission Electron ◽  
Feco Alloys ◽  
The Relationship ◽  
Microstructure And Magnetic Properties

Numerous studies have been conducted to develop next-generation recording technology in spintronics. Because ultrafine magneitc particles are vital components of the technology, the interplay between the microsturcture and magnetic properties has attracted attention extensively in recent years. We focused on the relationship between the microstructure and magnetic properties of Cu-Ni-X (X=Fe, Co, FeCo) alloys comprising nanogranular magnetic particles. In this work, we prepared Cu-20 at% Ni-5 at% (FeCo), Cu-20 at% Ni-5 at% Fe, Cu-20 at% Ni-5 at% Co and examined the changes of microstructure and magnetic properties associated with heat treatments and composition. To examaine microstructural evolution of the alloy specimens, we conducted transmission electron microscope observations (TEM) with the as-quenched specimens and those aged at at 773-1073 K. We also carried out magneto-thermo gravimetry (MTG) measurements, superconducting quantum interference device (SQUID) measurements, magnetoresistance (MR) measurements and first-principles calculations based on the Koster-Korringa-Rostker (KKR) method with the Coherent Potential Approximation (CPA), to investigate the magnetic properties. The present work confirmed that the microstructure significantly changed, depending on the composition and heat treatment conditions. The present work also revealed that the magnetic properties closely correlated with the microstructure of samples.

scholarly journals Structural complexity and the metal-to-semiconductor transition in lead telluride

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Iryna Zelenina ◽  
Paul Simon ◽  
Igor Veremchuk ◽  
Xinke Wang ◽  
Matej Bobnar ◽  
...  
Keyword(s):  
Lead Telluride ◽  
Structural Complexity ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Structural Defects ◽  
Dislocation Network ◽  
Lead Chalcogenides ◽  
Temperature Dependent ◽  
Transmission Electron ◽  
Increasing Temperature

AbstractLead chalcogenides are known for their thermoelectric properties since the first work of Thomas Seebeck on the discovery of this phenomenon. Yet, the electronic properties of lead telluride are still of interest due to the incomplete understanding of the metal-to-semiconductor transition at temperatures around  230 °C. Here, a temperature-dependent atomic-resolution transmission electron microscopy study performed on a single crystal of lead telluride reveals structural reasons for this electronic transition. Below the transition temperature, the formation of a dislocation network due to shifts of the NaCl-like atomic slabs perpendicular to {100} was observed. The local structure modification leads to the appearance of in-gap electronic states and causes metal-like electronic transport behavior. The dislocation network disappears with increasing temperature, yielding semiconductor-like electrical conductivity, and re-appears after cooling to room temperature restoring the metal-like behavior. The structural defects coupled to the ordering of stereochemically active lone pairs of lead atoms are discussed in the context of dislocations' formation.

scholarly journals Structural, electrical and magnetic properties of the pyrochlorate Er_2-x Sr_x Ru_2O_7 (0<=x<=0.10) system

2018 ◽  
Vol 64 (3) ◽  
pp. 222 ◽  
Author(s):  
Mohamed Abatal
Keyword(s):  
Magnetic Properties ◽  
Crystal Size ◽  
Rietveld Method ◽  
Ambient Pressure ◽  
Zero Field ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Electrical And Magnetic Properties ◽  
Increasing Temperature

In this research, we report a detailed study of the structural, electrial and magnetic properties of the ruthenium pyrochlore with the composition (Er_2-x Sr_x) Ru_2O_7 0<=x<=0.10 prepared by solid-state reaction in air at ambient pressure.  The synthesized products were characterized using powder X-ray diffraction. The structure of the samples was refined with the Rietveld method, showing that the lattice parameters are more sensitive to the Strontium and Erbium sites. Scanning electron microscopy shows that the crystal size varies between 0.27 and 0.62 mu m. In all polycrystalline samples, the electrical resistance decreases with increasing temperature, indicating that the samples are nonmetallic. The slope of the temperature-dependent resistance profiles systematically decreases with increasing x, proving that the carrier concentration increases with increasing the Sr content. Zero-field-cooled and field cooled magnetization measurements show an irreversible behavior where the split is systematically enhanced by increasing x.

scholarly journals Synthesis and Magnetic Properties of a Superparamagnetic Nanocomposite “Pectin-Magnetite Nanocomposite”

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Jude Namanga ◽  
Josepha Foba ◽  
Derek Tantoh Ndinteh ◽  
Divine Mbom Yufanyi ◽  
Rui Werner Maçedo Krause
Keyword(s):  
Electron Microscopy ◽  
Magnetic Properties ◽  
Magnetite Nanoparticles ◽  
Quantum Interference ◽  
Size Control ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Drying Conditions

Magnetic nanocomposites composed of superparamagnetic magnetite nanoparticles in a pectin matrix were synthesized by an in situ coprecipitation method. The pectin matrix acted as a stabilizer and size control host for the magnetite nanoparticles (MNPs) ensuring particle size homogeneity. The effects of the different reactant ratios and nanocomposite drying conditions on the magnetic properties were investigated. The nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FT-IR) spectroscopy, and superconducting quantum interference device magnetometer (SQUID). Superparamagnetic magnetite nanoparticles with mean diameters of 9 and 13 nm were obtained, and the freeze-dried nanocomposites had a saturation magnetization of 54 and 53 emu/g, respectively.

Structure and Magnetic Properties of Nanocrystalline Pd-Co and Pd-Co-Fe Layers

2007 ◽  
Vol 124-126 ◽  
pp. 907-910 ◽  
Author(s):  
András Kovács ◽  
Kazuhisa Sato ◽  
Yoshihiko Hirotsu
Keyword(s):  
Magnetic Properties ◽  
Quantum Interference ◽  
Alloy Formation ◽  
In Situ Tem ◽  
Superconducting Quantum Interference Device ◽  
Transmission Electron ◽  
Co Nanoparticles ◽  
Feco Nanoparticles ◽  
Fe Addition

The structure and magnetic properties of sequentially deposited Pd-Co and Pd-Co- Fe nanocrystals have been investigated by transmission electron microscopy (TEM) and superconducting quantum interference device magnetometer. The fcc structured PdCo alloy formation was found in binary Pd-Co nanostructured samples analysed by in situ TEM annealing. In ternary sample, the addition of Fe to Pd-Co resulted in a complex of Pd and FeCo nanoparticles. In situ TEM annealing of the ternary sample lead to the formation of L10 ordered phase. It was found that the magnetic properties of the nanoparticles were improved by Fe addition to the Pd-Co nanoparticles.

Y-Type Hexaferrites: Structural, Dielectric and Magnetic Properties

2012 ◽  
Vol 189 ◽  
pp. 209-232 ◽  
Author(s):  
Rajshree B. Jotania ◽  
Hardev Singh Virk
Keyword(s):  
Magnetic Properties ◽  
Quantum Interference ◽  
Room Temperature ◽  
Structural Changes ◽  
Ferromagnetic State ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Lcr Meter ◽  
Co Precipitation

This paper attempts to provide a historical survey of structure of various types of hexaferrites. It provides information about synthesis, characterization, structural, magnetic and dielectric properties of Y-type hexagonal ferrites using various chemical routes. We have prepared a series of cobalt doped Sr2Cu2-xCoxFe12O22(x = 0.0 to 1.0) hexaferrites using a wet chemical co-precipitation technique. The prepared hexaferrite precursors were calcined at 950 °C for 4 hours in a furnace and slowly cooled to room temperature. The crystal structure of Y-type hexaferrites is rather complicated. The chemical and structural changes were examined in detail by X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Scanning electron microscopy (SEM), and Fourier transform infra-red (FTIR) spectroscopy. X-ray diffraction studies showed that sintering temperature as low as 950°C was sufficient to produce a single-phase Y-type hexaferrite material. The dielectric measurements were carried out over the frequency range of 100 Hz to 2 MHz at room temperature using an LCR meter to study the variation of dielectric constant and loss tangent with frequency. The magnetic properties of hexaferrite samples were investigated using a vibration sample magnetometer (VSM), and a superconducting quantum interference device (SQUID) magnetometer in the temperature range 30K to 200K. A change from ferromagnetic state to super paramagnetic state has been observed in Co doped Sr2Cu2-xCoxFe12O22(x= 0.6 to 1.0) hexaferrite. The novel applications of all types of hexaferrite materials have been described.

Effect of Sputtering Input Power of Co on Structure and Magnetic Properties of Fe-Co-N Thin Films

2009 ◽  
Vol 79-82 ◽  
pp. 635-638 ◽  
Author(s):  
Xin Wang ◽  
Hui Jia ◽  
Wei Tao Zheng ◽  
Wei Xu ◽  
Bei Hong Long
Keyword(s):  
Thin Films ◽  
Magnetic Properties ◽  
Photoelectron Spectroscopy ◽  
Quantum Interference ◽  
Input Power ◽  
Superconducting Quantum Interference Device ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Composition Structure

Fe-Co-N thin films with various Co content were synthesized on Si (111) substrate using facing-target magnetron sputtering by changing sputtering input power on Co target. During deposition, the input power on Fe target was kept at 160 W. The composition, structure, and magnetic properties were examined by X-ray photoelectron spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and superconducting quantum interference device. XRD and TEM investigations showed that at lower input power of 11.2 W on Co target, the phases in the film were -(Fe,Co)4N and Co3N. Increasing sputtering input power, the content of Co in the film increased. At input power of 14 W, film contained -(Fe,Co)8N phase was produced which exhibited higher saturation magnetization (252.85 Am2/kg) and lower value of coercivity (3.66 kAm-1), corresponded to the 12% content of Co in the film.

Transport and Magnetic Properties of CrO2-Polymer Magnetic Composites

2008 ◽  
Vol 47-50 ◽  
pp. 326-330
Author(s):  
Viorel Sandu ◽  
Stelian Popa ◽  
C. Plapcianu ◽  
Elena Sandu ◽  
N. Hurduc ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Methyl Methacrylate ◽  
Room Temperature ◽  
Electric Transport ◽  
Temperature Dependent ◽  
Magnetic Composites ◽  
Tunneling Model ◽  
Poly Methyl Methacrylate ◽  
High Fields ◽  
Increasing Temperature

We report the transport and magnetic properties of sintered CrO2-polymer composites. In order to improve the elastic properties of the CrO2-based composites, we investigated two types of styrene-based copolymers: poly(methyl methacrylate)-styrene (9/1 and 5/5) and linear polysiloxaneg- styrene as well as poly(methyl methacrylate)–butadiene 9/1. The electric transport and magnetoresistance are consistent with the spin tunneling model at low temperatures but the contribution of spin independent channels becomes important at high temperature and high fields. All composites display ferromagnetism at room temperature with saturation at low fields and a slightly temperature-dependent coercive field for the samples grafted either with butadiene or with styrene except for CrO2-polysiloxane-g-styrene composite where it exponentially decreases with increasing temperature.

Investigations On In Situ Nanocrystallization And Magnetic Properties For Amorphous Fe78Si9B13 Ribbons

1999 ◽  
Vol 577 ◽  
Author(s):  
Xiangeheng Sun ◽  
A. Cabral-Prieto ◽  
M. Jose Yacaman ◽  
Wensheng Sun
Keyword(s):  
Amorphous Phase ◽  
Amorphous State ◽  
Field Pattern ◽  
Transmission Electron ◽  
Measurement Results ◽  
Optimum Annealing Temperature ◽  
Increasing Temperature ◽  
Differential Scanning Calorimeters ◽  
Nanocrystalline Phases

ABSTRACTThe amorphous state of ferromagnetic Fe78Si9B13 (Metglas 2605S-2) and its nanocrystallization were investigated by in situ transmission electron microscope (TEM), Xray diffraction (XRD), Mossbauer spectroscopy (MS), differential scanning calorimeters (DSC) and magnetic moment measurements. The Mössbauer spectrum exhibited an essentially symmetric hyperfine field pattern of 259KOe in as-quenched amorphous state at room temperature. The Curie and crystallization temperature were determined to be Tc=708K and Tx= 803K, respectively. The Tx value was in good agreement with DSC measurement results. The occupied fraction of the nanocrystalline phases of α-Fe(Si) and Fe2B at in situ optimum annealing temperature was about 57% and 43%, respectively. It is notable that the magnetization of the amorphous phase decreases more rapidly with increasing temperature than those of nanocrystalline ferromagnetism, suggesting the presence of the distribution of exchange interaction in the amorphous phase or high metalloid contents.

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