Magnetic Hardening of Mechanically Alloyed Pr2Co7

ABSTRACTThe Pr2Co7 alloys are known to crystallize in two polymorphic forms: a hexagonal of the Ce2Ni7 type structure and a rhombohedral of the Gd2Co7 one. They were synthesized by mechanical milling and subsequent annealing in high vacuum. In this work, we focus on the structural study of these phases using X-ray diffraction and transmission electron microscopy. Also, we present the evolution of magnetic properties of these compounds vs the annealing temperature. The coercivity increases with annealing temperature reaching a maximum for TA = 800 °C. The highest is equal to 18 kOe at 293 K and 23 kOe at 10 K. The high magnetic properties observed in these nanostructured Pr2Co7 intermetallic alloys have their origin in its relatively high uniaxial magnetocrystalline anisotropy field, and in the homogeneous nanostructure developed by mechanical milling process and subsequent annealing. This high coercivity is attributed to the high anisotropy field of the Pr2Co7 phase and its nanoscale grain size. This leads to the formation of a magnetically hard Pr2Co7 phase.

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Influence of Alloying Additions on Enhancement of Soft Magnetic Properties Effect and Crystallization in FeXSiB (X=Cu, V, Co, Zr, Nb) Amorphous Alloys

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.130.171 ◽

2007 ◽

Vol 130 ◽

pp. 171-174 ◽

Cited By ~ 3

Author(s):

Z. Stokłosa ◽

G. Badura ◽

P. Kwapuliński ◽

Józef Rasek ◽

G. Haneczok ◽

...

Keyword(s):

Magnetic Properties ◽

Amorphous Alloys ◽

Crystallization Process ◽

Annealing Temperature ◽

Magnetic Measurements ◽

X Ray Diffraction ◽

Soft Magnetic ◽

X Ray ◽

Second Stage ◽

Transmission Electron

The crystallization and optimization of magnetic properties effects in FeXSiB (X=Cu, V, Co, Zr, Nb) amorphous alloys were studied by applying X-ray diffraction methods, high resolution transmission electron microscopy (HRTEM), resistometric and magnetic measurements. The temperatures of the first and the second stage of crystallization, the 1h optimization annealing temperature and the Curie temperature were determined for different amorphous alloys. Activation energies of crystallization process were obtained by applying the Kissinger method. The influence of alloy additions on optimization effect and crystallization processes was carefully examined.

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The Influence of Annealing Temperature on the Magnetic Properties of Mn0.5Co0.5Fe2O4 Nanoferrites Synthesized via Mechanical Milling Method

Journal of Superconductivity and Novel Magnetism ◽

10.1007/s10948-012-1878-5 ◽

2012 ◽

Vol 26 (4) ◽

pp. 1361-1367 ◽

Cited By ~ 3

Author(s):

H. M. I. Abdallah ◽

T. Moyo

Keyword(s):

Magnetic Properties ◽

Mechanical Milling ◽

Annealing Temperature ◽

Milling Method

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Influence of The Alloy Composition on The Magnetic Properties of Nanocrystalline Fe80M7B12Cu1 (M: Ti, Ta, Nb, Mo)

MRS Proceedings ◽

10.1557/proc-577-487 ◽

1999 ◽

Vol 577 ◽

Cited By ~ 5

Author(s):

M. Kopcewicz ◽

A. Grabias ◽

B. Idzikowski

Keyword(s):

Magnetic Properties ◽

Annealing Temperature ◽

Alloy Composition ◽

Anisotropy Field ◽

Nanocrystalline Phase ◽

Soft Magnetic Properties ◽

Soft Magnetic ◽

Scanning Calorimetry ◽

Rf Magnetic Field ◽

Collapse Effect

ABSTRACTFormation of the nanocrystalline bcc Fe phase due to thermal treatment of the amorphous Fe80M7B12Cu1 (M: Ti, Ta, Nb, Mo) precursors is studied by the Mössbauer and differential scanning calorimetry techniques. The dependence of the formation of the bcc Fe phase on the alloy composition is discussed. In order to determine the optimal soft magnetic properties of these nanocrystalline alloys the rf-Mössbauer technique is used in which rf collapse effect induced by a radio-frequency (rf) magnetic field is employed. It was found that anisotropy fields in the nanocrystalline phase were smaller in Nb- and Mo-containing alloys as compared to the alloys which contain Ti or Ta. Variations of the anisotropy field vs. alloy composition and annealing temperature are discussed in detail.

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Ultra-high-vacuum, high-resolution Transmission Electron Microscopy at 400 kV

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144498 ◽

1986 ◽

Vol 44 ◽

pp. 606-609

Author(s):

F. A. Ponce ◽

S. Suzuki ◽

H. Kobayashi ◽

Y. Ishibashi ◽

Y. Ishida ◽

...

Keyword(s):

Electron Microscopy ◽

High Vacuum ◽

Milling Process ◽

Electron Bombardment ◽

Ultra High Vacuum ◽

Specimen Preparation ◽

Ion Milling ◽

Transmission Electron ◽

Preparation Stage ◽

Resolution Imaging

Electron microscopy in an ultra high vacuum (UHV) environment is a very desirable capability for the study of surfaces and for near-atomic-resolution imaging. The existence of amorphous layers on the surface of the sample generally prevents the direct observation of the free surface structure and limits the degree of resolution in the transmission electron microscope (TEM). In conventional TEM, these amorphous layers are often of organic nature originating from the electron bombardment of hydrocarbons in the vicinity of the sample. They can in part also be contaminants which develop during the specimen preparation and transport stages. In the specimen preparation stage, contamination can occur due to backsputtering during the ion milling process. In addition, oxide layers develop from contact to air during transport to the TEM. In order to avoid these amorphous overlayers it is necessary: i) to improve the vacuum of the instrument, thus the need for ultra high vacuum; and ii) to be able to clean the sample and transfer it to the column of the instrument without breaking the vacuum around the sample.

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Elaboration of Single Crystalline AU/NI80FE20/CU/NI80FE20/NIO(111) Spin Valves

MRS Proceedings ◽

10.1557/proc-619-91 ◽

2000 ◽

Vol 619 ◽

Author(s):

C. Mocuta ◽

A. Barbier ◽

S. Lafaye ◽

P. Bayle-Guillemaud

Keyword(s):

Magnetic Properties ◽

Giant Magnetoresistance ◽

Magnetic Layer ◽

Growth Conditions ◽

Spin Valves ◽

High Coercivity ◽

Magnetic Exchange ◽

Transmission Electron ◽

Magnetic Exchange Coupling

ABSTRACTThe successful preparation of fully epitaxial spin-valves elaborated on NiO(111) single crystals is reported. The growth conditions of a smooth 2D permalloy (Py = Ni80Fe20) layer have been determined. A very strong magnetic exchange interaction is evidenced on the Py/NiO(111) interface. It strongly modifies the magnetic properties of Py that acquires high coercivity, leaving it as a hard magnetic material. The second Py layer has unchanged magnetic properties and plays the role of the sensing soft magnetic layer. A giant magnetoresistance (GMR) of 3.5% at room temperature was easily obtained without optimizing the thickness of the different layers. Complementarily energy-filtered (EF-) and high-resolution (HR-) transmission electron microscopy (TEM) were used to fully characterize the spin valves. Within the framework of magnetic exchange coupling, our results open the possibility to elaborate model spin valves in which the role of each interface can be investigated and controlled at the atomic level. The detrimental effect of an inter-diffusion at the Py/NiO interface is evidenced.

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Mössbauer and magnetization studies of mechanically milled nanocrystalline Fe1–xAlx alloys

Canadian Journal of Physics ◽

10.1139/cjp-2014-0685 ◽

2015 ◽

Vol 93 (11) ◽

pp. 1257-1263

Author(s):

S. Rajan ◽

R. Shukla ◽

A. Kumar ◽

A. Vyas ◽

S. Khan ◽

...

Keyword(s):

Magnetic Properties ◽

Magnetic Behavior ◽

High Energy ◽

Milling Process ◽

Transmission Electron ◽

Bulk Magnetization ◽

Hyperfine Field Distributions ◽

Equilibrium Process ◽

Energy Ball ◽

Evolution Of Microstructure

Changes in the magnetic behavior of Fe1–xAlx (x = 0.3, 0.4, 0.5, 0.6) powders during mechanical alloying have been studied. The ball milling process leads to formation of solid state reaction assisted by severe plastic deformation because of which crystallite size is reduced and as a result of which interesting magnetic properties are developed. The evolution of magnetic order in high-energy ball-milled Fe–Al solid solution is investigated using 57Fe Mössbauer spectroscopy and vibrating sample magnetometer. Mössbauer spectra and the hyperfine field distributions of all the samples show the presence of both magnetic and paramagnetic components in the samples. The corresponding bulk magnetization studies also show that the Al rich samples are also ferromagnetic, which can be attributed to the presence of disordered Fe-rich phases due to the non-equilibrium process of alloying. In Fe-rich samples, the formation of an off stoichiometric Fe3Al phase is favored while in the case of Al-rich samples both Al-rich phases and clustering of Fe and Al atoms are present. The systematic variation in the magnetic properties has been qualitatively correlated with the evolution of microstructure, reduction in grain size (obtained using transmission electron microscopy) and enhanced intergranular exchange coupling.

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DSC-TGA Hydrogen Evaluation during Mechanical Milling of AlFe Intermetallic

Materials Science Forum ◽

10.4028/www.scientific.net/msf.755.105 ◽

2013 ◽

Vol 755 ◽

pp. 105-110 ◽

Cited By ~ 3

Author(s):

E. García de León M. ◽

O. Téllez-Vázquez ◽

C. Patiño-Carachure ◽

G. Rosas

Keyword(s):

Mechanical Milling ◽

Milling Time ◽

Hydrogen Generation ◽

Pure Aluminum ◽

High Energy ◽

Milling Process ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

Diffraction Patterns

Fe40Al60 (at%) intermetallic alloy composition was obtained by conventional casting methods and subsequently subjected to high-energy mechanical milling under different conditions of humidity. All samples were characterized by X-ray diffraction patterns (XRD), transmission electron microcopy (TEM) and DSC-TGA thermogravimetric experiments. After the milling process, the amount of hydrogen generated was determined using thermogravimetric analysis and chemical reactions (stoichiometry). All techniques confirm the formation of bayerite phase which is attributed to the hydrogen embrittlement reaction between the intermetallic material and water to release hydrogen. It was observed that the hydrogen generation is increased as the ball milling time is increased. The quantity of hydrogen evaluated is similar to that obtained in previous reported experiments with pure aluminum and some of its alloys.

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Structural Changes in Nickel Silicide Thin Films under the Presence of Al and Ga

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.2938 ◽

2010 ◽

Vol 638-642 ◽

pp. 2938-2943 ◽

Cited By ~ 4

Author(s):

A.V. Mogilatenko ◽

Frank Allenstein ◽

M.A. Schubert ◽

Meiken Falke ◽

G. Beddies ◽

...

Keyword(s):

Electron Microscopy ◽

Thin Films ◽

Transmission Electron Microscopy ◽

Room Temperature ◽

Structural Changes ◽

Annealing Temperature ◽

Nickel Silicide ◽

Subsequent Annealing ◽

Formation Temperature ◽

Transmission Electron

Thin Ni/Al and Ni/Ga layers of different atomic ratios were codeposited onto Si(001) at room temperature followed by subsequent annealing. Influence of annealing temperature on morphology and composition of ternary disilicide NiSi2-xAlx and NiSi2-xGax layers was investigated by transmission electron microscopy. Addition of Al or Ga leads to a decrease of the disilicide formation temperature from 700°C down to at least 500°C. Depending on the composition closed, uniformly oriented NiSi2-xAlx and NiSi2-xGax layers were observed after annealing at 900°C, whereas reaction of a pure Ni film with Si leads to the island formation with a mixture of A- and B-type orientations.

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