Giant Magnetoresistance in Annealed Fe/Cr Multilayers

1993 ◽  
Vol 313 ◽  
Author(s):  
Noa More Rensing ◽  
Bruce M. Clemens
Keyword(s):  
Giant Magnetoresistance ◽  
Structural Effect ◽  
Magnetic Effect ◽  
Antiferromagnetic Coupling ◽  
X Ray Diffraction ◽  
Magnetoresistance Effect ◽  
X Ray ◽  
Giant Magnetoresistance Effect ◽  
Higher Temperature ◽  
Spin Dependent Scattering

ABSTRACTThe giant magnetoresistance effect in antiferromagnetically coupled Fe/Cr Multilayers has been attributed to spin dependent scattering at the interfaces between the constituents. One possible source of this spin dependent scattering is chromium impurities in the iron layers due to intermixing at the interfaces. Annealing the films can promote the diffusion of the components, increasing the impurity concentration and therefore the Magnetoresistance. For this study Fe/Cr Multilayers were annealed at several temperatures and for several durations. Annealing at moderate temperatures (∼ 350°C) increases the Magnetoresistance, while higher temperature anneals (∼ 600°C) cause the magnetoresistance to disappear completely. Long anneals at 330°C (> 100 hours) also reduce the Magnetoresistance. VSM Measurements indicate that the antiferromagnetic coupling is reduced in the annealed samples but show no evidence of Magnetically “dead” alloy layers. Low angle X-ray diffraction indicates that the structural effect of annealing is very subtle in comparison to the significant magnetic effect.

Exchange Coupling and Giant Magnetoresistance in Electrodeposited Co/Cu Multilayers

1997 ◽  
Vol 475 ◽  
Author(s):  
A. Dinia ◽  
K. Rahmouni ◽  
G. Schmerber ◽  
H. El Fanity ◽  
M. Bouanani ◽  
...  
Keyword(s):  
Exchange Coupling ◽  
Giant Magnetoresistance ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Magnetoresistance Effect ◽  
X Ray ◽  
Resistivity Measurements ◽  
Fee Structure ◽  
Giant Magnetoresistance Effect ◽  
Spacer Layer

ABSTRACTWe present the results of the transport and magnetization measurements of electrodeposited Co/Cu multilayers grown in a single electrolyte based on C0SO4, H3BO3 and CuSO4. The samples are deposited on glass substrate covered by a 500 Å thick Cu buffer layer. X-ray diffraction performed on the samples shows fee structure of both Co and Cu layers with preferential (111) orientation. Resistivity measurements show a giant magnetoresistance effect of about 4% at room temperature for multilayers with Co and Cu thickness between 4 nm ≤ tco ≤ 6 nm and 3 nm ≤ tcu ≤4 nm respectively. For Co thickness tCo ≤ 15 nm, the magnetoresistance completely vanishes indicating that there is no more continuous Co layer. The indirect antiferromagnetic exchange coupling between magnetic Co layers is relatively large for 4 nm thick Cu spacer layer and gives rise to a temperature dependence of about 30% between room temperature and 4.2 K.

Annealing of CoxCu1-x / Cu Multilayers

2002 ◽  
Vol 746 ◽  
Author(s):  
Jörg Ebert ◽  
Mohammad Ghafari ◽  
Branko Stahl ◽  
Horst Hahn
Keyword(s):  
Giant Magnetoresistance ◽  
Structural Changes ◽  
Rapid Decrease ◽  
Interface Roughness ◽  
Antiferromagnetic Coupling ◽  
Bilayer Thickness ◽  
Magnetoresistance Effect ◽  
X Ray ◽  
Giant Magnetoresistance Effect ◽  
Magnetic Layers

ABSTRACTIn the multilayer system cobalt / copper at the second antiferromagnetic coupling maximum (2. AFM) with a copper thickness of dCu = 2,2 nm it is possible to reduce magnetoresistive hysteresis by the use of either very thin Co-layers or by alloyed magnetic layers Co1-xCux. It was possible to achieve values for the giant magnetoresistance effect of GMR ≈ 20 % for as prepared samples. A heat treatment was applied to study the degeneration of the system. For annealing at moderate temperatures (Tanneal ≤ 250°C) an increase up to GMR ≈ 25 % was observed. Annealing at slightly higher temperatures lead to an rapid decrease in the GMR effect. To study the structural changes the method of x-ray reflectivity was utilized showing changes in interface roughness as well as in bilayer thickness.

A QUANTUM MODEL FOR THE GIANT MAGNETORESISTANCE EFFECT

1996 ◽  
Vol 10 (17) ◽  
pp. 2103-2110
Author(s):  
LEI ZHOU ◽  
RUIBAO TAO
Keyword(s):  
Simple Model ◽  
Electric Conductivity ◽  
Giant Magnetoresistance ◽  
Quantum Model ◽  
Magnetoresistance Effect ◽  
Conduction Electrons ◽  
Giant Magnetoresistance Effect ◽  
Model Hamiltonian ◽  
Spin Dependent Scattering ◽  
Scattering Potential

A quantum explanation based on the previous semi-classical theory has been presented for the giant magnetoresistance (GMR) effect in this letter. A simple model Hamiltonian has been proposed for the conduction electrons in the magnetic layered structures in which the interaction of the conduction electrons with the local spins and the spin-dependent scattering potential have been considered, then an analytical expression of the effective electric conductivity is derived after some simplifying procedures. The main feature of the GMR effect may be explained by this simple model qualitatively.

Photoresist-buffer-enhanced antiferromagnetic coupling and the giant magnetoresistance effect of Co/Cu multilayers

2008 ◽  
Vol 20 (45) ◽  
pp. 452202 ◽  
Author(s):  
Yuan-fu Chen ◽  
Yongfeng Mei ◽  
Angelo Malachias ◽  
Jens Ingolf Mönch ◽  
Rainer Kaltofen ◽  
...  
Keyword(s):  
Giant Magnetoresistance ◽  
Antiferromagnetic Coupling ◽  
Magnetoresistance Effect ◽  
Giant Magnetoresistance Effect

Quantitative X-Ray Diffraction From Superlattices

MRS Bulletin ◽  
1992 ◽  
Vol 17 (12) ◽  
pp. 33-38 ◽  
Author(s):  
Eric E. Fullerton ◽  
Ivan K. Schuller ◽  
Y. Bruynseraede
Keyword(s):  
Physical Properties ◽  
Giant Magnetoresistance ◽  
Growth Conditions ◽  
Antiferromagnetic Coupling ◽  
X Ray Diffraction ◽  
Entire Cross Section ◽  
Cross Sectional ◽  
X Ray ◽  
Superlattice Structure ◽  
Wide Range

The physical properties of superlattices have been the subject of considerable interest because a wide range of phenomena associated with very thin films, interfaces, and coupling effects can be studied. Recent areas of activity in metallic superlattices include antiferromagnetic coupling of ferromagnetic layers across nonmagnetic spacer layers, giant magnetoresistance, magnetic surface anisotropy, low-dimensional superconductivity, and anomalous mechanical properties. All of these phenomena are strongly affected by the chemical and physical properties of the individual layers and by the superlattice structure. Therefore, a detailed understanding of the properties of superlattices requires a nondestructive, quantitative determination of the superlattice structure.Because superlattices are not in thermodynamic equilibrium, their structure is sensitive to preparation methods and growth conditions. A dramatic example of superlattice structural dependence on growth conditions is shown in Figure 1, for sputtered Nb/Si superlattices. Increasing the Ar pressure during sputtering decreases the kinetic energy of the deposited atoms, thereby changing their surface mobility, and thus altering growth dynamics. Figure 1 shows the low-angle x-ray diffraction and cross-sectional transmission electron microscopy (TEM) images of [Nb(35 Å)/Si(25 Å)]40, superlattices sputtered in, respectively, 3 and 15 mTorr of Ar. The TEM image of the 3 mTorr superlattice clearly shows the smooth and continuous layering across the entire cross section of the image (≈5 μm). This is characteristic of sputtered metal/semiconductor superlattices used for x-ray optics.

Stress in Sputtered Co90Fe10/Ag GMR Multilayers

1996 ◽  
Vol 436 ◽  
Author(s):  
J. D. Jarratt ◽  
V. R. Inturi ◽  
J. L. Weston ◽  
J. A. Barnard
Keyword(s):  
Giant Magnetoresistance ◽  
Room Temperature ◽  
Multilayer Films ◽  
Antiferromagnetic Coupling ◽  
High Temperature Annealing ◽  
X Ray Diffraction ◽  
Hexagonal Symmetry ◽  
Individual Layer ◽  
X Ray ◽  
The Difference

AbstractStress, giant magnetoresistance (GMR), structure, and magnetic properties of sputtered (Co90Fe10X Å/Ag Y Å)×20 multilayer films have been investigated at room temperature where X ranges from 7.5 to 25 Å and Y from 10 to 60 Å. These films exhibit distinct GMR behaviors dependent on individual layer thicknesses, including layered granular-type GMR in CoFe 7.5 Å samples and ‘discontinuous’ GMR (DGMR) in CoFe 15 and 25 Å samples with Ag thicknesses over 30 Å. No antiferromagnetic coupling was observed. CoFe 10 Å samples act as a transition between GMR behaviors. Compressive stress decreases with increasing Ag thickness in the CoFe 7.5 Å samples. In the CoFe 15 and 25 Å samples the stress fluctuates similarly depending on Ag thickness. The difference in stress and MR behavior between the CoFe 7.5 Å and the 15 and 25 Å samples is thought to be due to incomplete CoFe layering in the CoFe 7.5 Å samples. In the CoFe 15 Å DGMR samples, high temperature annealing resulted in tensile stresses large enough to cause film detachment. X-ray diffraction reveals a strong (111) growth texture as well as satellite peaks from coherent layering. This (111) texture is also evidenced by patterns with hexagonal symmetry formed by the detached films.

scholarly journals Impact of high temperatures on aluminoceladonite studied by Mössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopy

2021 ◽  
Author(s):  
Mariola Kądziołka-Gaweł ◽  
Maria Czaja ◽  
Mateusz Dulski ◽  
Tomasz Krzykawski ◽  
Magdalena Szubka
Keyword(s):  
Photoelectron Spectroscopy ◽  
Integral Intensity ◽  
Photoelectron Spectra ◽  
X Ray Diffraction ◽  
Structural Reorganization ◽  
Oh Groups ◽  
X Ray ◽  
Al Content ◽  
Integral Intensity Ratio ◽  
Higher Temperature

AbstractMössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopies were used to examine the effects of temperature on the structure of two aluminoceladonite samples. The process of oxidation of Fe2+ to Fe3+ ions started at about 350 °C for the sample richer in Al and at 300 °C for the sample somewhat lower Al-content. Mössbauer results show that this process may be associated with dehydroxylation or even initiate it. The first stage of dehydroxylation takes place at a temperature > 350 °C when the adjacent OH groups are replaced with a single residual oxygen atom. Up to ~500 °C, Fe ions do not migrate from cis-octahedra to trans-octahedra sites, but the coordination number of polyhedra changes from six to five. This temperature can be treated as the second stage of dehydroxylation. The temperature dependence on the integral intensity ratio between bands centered at ~590 and 705 cm−1 (I590/I705) clearly reflects the temperature at which six-coordinated polyhedra are transformed into five-coordinated polyhedra. X-ray photoelectron spectra obtained in the region of the Si2p, Al2p, Fe2p, K2p and O1s core levels, highlighted a route to identify the position of Si, Al, K and Fe cations in a structure of layered silicates with temperature. All the measurements show that the sample with a higher aluminum content and a lower iron content in octahedral sites starts to undergo a structural reorganization at a relatively higher temperature than the less aluminum-rich sample does. This suggests that iron may perform an important role in the initiation of the dehydroxylation of aluminoceladonites.

Study of Low-Grade Nickel Laterite Processing Using Palm Shell Charcoal as Reductant

2020 ◽  
Vol 1000 ◽  
pp. 436-446
Author(s):  
Bambang Suharno ◽  
Nolzha Primadha Ilman ◽  
Achmad Shofi ◽  
Deni Ferdian ◽  
Fajar Nurjaman
Keyword(s):  
Sodium Sulfate ◽  
Selective Reduction ◽  
Reduction Process ◽  
Low Grade ◽  
X Ray Diffraction ◽  
X Ray ◽  
Palm Shell ◽  
Higher Temperature ◽  
Nickel Grade

This study was conducted to investigate the effect of palm shell charcoal reductant in the selective reduction of nickel ore with the addition of additive at various temperatures and times. In this present work, 10 wt. % of sodium sulfate as additive and 5, 10, 15 wt. % of palm shell charcoal as reductants were used. The reduction of nickel ore was performed at 950oC, 1050oC, and 1150oC for 60, 90, and 120 minutes. A wet magnetic separation method was then carried out to separate the concentrates and tailings. Characterization of reduced ore was performed by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), while the composition of ferronickel in concentrate was identified by X-Ray Fluorescence (XRF). The result showed that the higher temperature reduction, the higher of nickel grade, and its recovery at the concentrate. Nevertheless, the longer reduction time and the more reductant in nickel ore lowering the nickel grade and its recovery in the concentrate. The optimum condition in this selective reduction process was obtained with the addition of 5 wt. % of reductant and 10 wt. % of sodium sulfate in nickel ore, which was reduced at 1150oC for 60 minutes. It resulted in 4.60% and 73.23% for nickel grade and its recovery, respectively.

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