Investigation on the Origin of Magnetization in Plastically Deformed NI51TI49 Alloy

The article deals with the investigation of structure and magnetic properties of plastically deformed Ni51Ti49 alloy. The magnetic hysteresis loops confirm the presence of ferromagnetic properties in the alloy. The transmission electron microscopy (TEM) detects the appearance of lenticular crystals with bending contours which indicate the large distortion of the crystal lattice. The crystal lattice curvature occurs due to the large atom displacement. As a result, icosahedral clusters with the Frank-Kasper (FK) structure can be formed. The spin-polarized density of electron states and the magnetic moments for both non-deformed (near-spherical structure) and deformed (elongated by 5% along the Z-axis) Ni7Ti5 (FK-12), Ni8Ti5 (FK-13), and Ni10Ti6 (FK-16) clusters are calculated for the explanation of possibility of magnetization appearance in Ni51Ti49 alloy. The calculations show the increase in the magnetic moments for the deformed clusters. The calculated spectra demonstrate the high density of electron states near the Fermi level which is a characteristic feature of ferromagnetic alloys.

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Fe-Core/Au-Shell Nanoparticles: Growth Mechanisms, Oxidation and Aging Effects

MRS Proceedings ◽

10.1557/proc-0887-q07-04 ◽

2005 ◽

Vol 887 ◽

Cited By ~ 1

Author(s):

Kai Liu ◽

Sung-Jin Cho ◽

Susan M. Kauzlarich ◽

J. C. Idrobo ◽

Joseph E. Davies ◽

...

Keyword(s):

Electrical Transport ◽

Inductively Coupled Plasma ◽

Magnetic Moments ◽

Hysteresis Loops ◽

Growth Mechanisms ◽

Aging Effects ◽

Contrast Imaging ◽

Shell Nanoparticles ◽

Transmission Electron ◽

Over Time

ABSTRACTWe report the chemical synthesis of Fe-core/Au-shell nanoparticles (Fe/Au) by a reverse micelle method, and the investigation of their growth mechanisms and oxidation-resistant characteristics. The core-shell structure and the presence of the Fe and Au phases have been confirmed by transmission electron microscopy, energy dispersive spectroscopy, x-ray diffraction, Mössbauer spectroscopy, and inductively coupled plasma techniques. Additionally, atomic-resolution Z-contrast imaging and electron energy loss spectroscopy in a scanning transmission electron microscope have been used to study details of the growth processes. The Au-shells grow by nucleating on the Fe-core surfaces before coalescing. First-order reversal curves, along with the major hysteresis loops of the Fe/Au nanoparticles have been measured as a function of time in order to investigate the evolution of their magnetic properties. The magnetic moments of such nanoparticles, in the loose powder form, decrease over time due to oxidation. The less than ideal oxidation-resistance of the Au shell may have been caused by the rough Au surfaces. In a small fraction of the particles, off-centered Fe cores have been observed, which are more susceptible to oxidation. However, in the pressed pellet form, electrical transport measurements show that the particles are fairly stable, as the resistance and magnetoresistance of the pellet do not change appreciably over time. Our results demonstrate the complexity involved in the synthesis and properties of these heterostructured nanoparticles.

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Microstructure and Magnetic Behavior of One-Dimensional Co0.5Zn0.5Fe2O4 Nanofibers

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.284-286.861 ◽

2011 ◽

Vol 284-286 ◽

pp. 861-865

Author(s):

Jun Xiang ◽

Guang Zhen Zhou ◽

Yan Qiu Chu ◽

Xiang Qian Shen

Keyword(s):

Electron Microscopy ◽

Sol Gel ◽

Magnetic Hysteresis ◽

Hysteresis Loops ◽

Magnetic Behavior ◽

Average Diameter ◽

Diffraction Field ◽

One Dimensional ◽

Morphological Variations ◽

Transmission Electron

One-dimensional Co0.5Zn0.5Fe2O4 nanostructures (nanofibers) with an average diameter of 154 nm were fabricated by electrospinning. These nanofibers were characterized by X–ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Magnetic hysteresis loops were measured for randomly oriented and aligned Co0.5Zn0.5Fe2O4 nanofibers, in comparison with the corresponding powder sample synthesized using the conventional sol-gel process. The differences in magnetic properties are observed between the Co0.5Zn0.5Fe2O4 nanofibers and powders, and these differences mainly arise from the grain size and morphological variations between these two materials. In determining the magnetization ease axis for the aligned Co0.5Zn0.5Fe2O4 nanofibers the shape anisotropy is slightly dominant competing with the magnetocrystalline anisotropy.

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Preparation and Properties of Zn1-XCoxO Magnetic Microspheres

Materials Science Forum ◽

10.4028/www.scientific.net/msf.663-665.1081 ◽

2010 ◽

Vol 663-665 ◽

pp. 1081-1084

Author(s):

Zhi Fu Liu ◽

Qing Hong Zhang ◽

Li Yun Chen ◽

Yao Gang Li ◽

Hong Zhi Wang

Keyword(s):

Electron Microscopy ◽

Room Temperature ◽

Magnetic Hysteresis ◽

Hysteresis Loops ◽

Magnetic Microspheres ◽

Diffraction Field ◽

Vibrating Sample Magnetometry ◽

X Ray ◽

Transmission Electron ◽

Magnetic Hysteresis Loops

Zn1-xCoxO magnetic microspheres have been synthesized by a simple solvothermal process. Different Co2+ dopant concentrations have been used as modifier and proved to be efficient at controlling the morphology and magnetic property of Zn1-xCoxO microspheres. The as-synthesized samples are characterized by X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, photoluminescence spectrophotometer and vibrating sample magnetometry. Magnetic hysteresis loops reveal the samples exhibit ferromagnetic loops at room temperature. The meta-saturation magnetization value and coercivity of Zn0.8Co0.2O reach 0.09 emu·g-1 and 15.0 Oe.

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Structure and Magnetic Properties of Ga Substituted Ni-Ferrites

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.446-447.68 ◽

2013 ◽

Vol 446-447 ◽

pp. 68-72

Author(s):

Ahmad Amirabadizadeh ◽

Zobedeh Momeni Larimi ◽

Saeideh Eghbali

Keyword(s):

Magnetic Properties ◽

Single Phase ◽

Sol Gel ◽

Magnetic Hysteresis ◽

Hysteresis Loops ◽

X Ray Diffraction ◽

Auto Ignition ◽

Transmission Electron ◽

Magnetic Hysteresis Loops ◽

Ga Content

Nanocrystalline Ga doped nickel ferrite [(NiFe2-xGaxO4 (x=0.0, 0.1, 0.3, 0.5 and 0.7)] powders have been synthesized by sol-gel auto-ignition method and the effect of non-magnetic gadillum content on the nanosize particles and magnetic properties has been studied. The X-ray diffraction (XRD) revealed that the powders obtained are single phase with spinel structure. The calculated grain size from XRD data have been verified using transmission electron microscopy (TEM). TEM photograph shows that the powders consist of nanometer sized grain. The size of nanoparticles decreases as the non magnetic Ga content increases. Magnetic hysteresis loops were measured at room temperature with maximum applied magnetic field of 20 KOe. As Ga content increases, the measured magnetic hysteresis curves became border and saturation magnetization (MS) increased up to x= 0.3 and further increase of x leads the magnetization to decrease. The results are explained according to the assumed cation distribution.

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Structure and Magnetic Properties of Fe-Doped TiO2 Nano-Crystals by Nonaqueous Synthesis

Materials Science Forum ◽

10.4028/www.scientific.net/msf.663-665.883 ◽

2010 ◽

Vol 663-665 ◽

pp. 883-889

Author(s):

Chu Feng Li ◽

Ling Yue ◽

Wen Jin ◽

Ting Zhang ◽

Huan Wang ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Photoelectron Spectroscopy ◽

Anatase Phase ◽

Magnetic Hysteresis ◽

Hysteresis Loops ◽

X Ray ◽

Transmission Electron ◽

Crystallite Sizes ◽

Nonaqueous Synthesis

Ti1-xFexO2 nanocrystals with x = 0.01, 0.02, 0.03 were prepared via a nonaqueous synthesis route. X-ray diffraction, transmission electron microscopy and high resolution transmission electron microscopy characterization confirmed the formation of anatase-phase nanocrystals with the average crystallite sizes of around 10 nm. The lattice constants alternate with the increase of the Fe content and no iron clusters were generated. X-ray photoelectron spectroscopy measurements showed that the substitutional Fe ions present mainly the valence of +3. The magnetic hysteresis loops measured at room temperature (RT) 300K showed that all the doped samples are atypically ferromagnetic, and the coercivity (Hc) of all the Fe-doping samples is around 0.1 T. An interpretation for the intrinsic RT ferromagnetism is put up based on the free carriers and defects induced interaction between Fe3+ ions.

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High-field slope correction of hysteresis loops: are we doing it correctly?

10.5194/egusphere-egu2020-13109 ◽

2020 ◽

Author(s):

Xiang Zhao ◽

Andrew Roberts ◽

David Heslop

Keyword(s):

Applied Field ◽

High Field ◽

Magnetic Moments ◽

Magnetic Hysteresis ◽

Hysteresis Loops ◽

Magnetic Studies ◽

Magnetic Components ◽

Slope Correction ◽

Linear Slope ◽

Mineral Magnetic

Presentation of magnetic hysteresis data has long been a standard component of paleomagnetic, rock magnetic, and environmental magnetic publications. It has become standard practice to correct the high-field slope of hysteresis loops using a line fit through data points between 70 and 100% of the maximum applied field. Implicit to this approach is that the magnetization is considered saturated if the loop is closed at the point at which 70% of the maximum applied field is reached. This approach treats hysteresis overly simplistically because it assumes that the irreversible magnetization, which is what gives rise to hysteresis, is the only relevant part of the magnetization. The reversible component of magnetization is also important; this component approaches saturation non-linearly following the so-called law of approach to saturation, where the magnetization continues to increase due to rotation of magnetic moments parallel to the applied field, which is resisted by the anisotropy of the material. Various mathematical formulations exist for the law of approach to saturation. Use of this law is not straightforward for geological materials because terms in the respective equations depend on the material analysed and must be approximated, which becomes problematical for samples with mixed magnetic components. Alternatively, hysteresis loops can be fitted and extrapolated to high fields to estimate the approach to saturation using hyperbolic functions. We illustrate issues associated with linear slope correction at 70&#8211;100% of the maximum applied field by comparing hysteresis parameters estimated using approach to saturation fitting with various maximum applied fields. In all cases, for maximum fields used typically in mineral magnetic studies (e.g., 1 T), conventional slope correction underestimates the saturation magnetization Ms&#160;and overestimates the ratio of the saturation remanent magnetization Mrs&#160;to Ms. Hysteresis loop undersaturation is likely to be widespread in mineral magnetic studies with inadequate slope correction probably causing a large uncertainty in published hysteresis parameters. We recommend routine application of approach to saturation fitting of hysteresis loops, which can help to better estimate Ms&#160;and Mrs/Ms, as well as help to indicate whether a maximum applied field is sufficient to achieve magnetic saturation.

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