Electromigration Reliability Study of a GMR Spin Valve Device

1999 ◽  
Vol 563 ◽  
Author(s):  
S. Shingubara ◽  
Y. Takeda ◽  
H. Sakue ◽  
T. Takahagi ◽  
A. H. Verbruggen
Keyword(s):  
Thermal Gradient ◽  
Elevated Temperatures ◽  
Spin Valve ◽  
Ferromagnetic Layer ◽  
Magnetization Vector ◽  
Atomic Diffusion ◽  
Thermal Probe ◽  
Reliability Study ◽  
Current Densities ◽  
Dc Current

AbstractElectromigration reliability of a GMR spin valve device has been investigated at elevated temperatures at various DC current densities. Significant degradation of the magnetoresistance was observed when the current density was higher than 20 MA/cm2. Either the electromigration induced damage or the rotation of the magnetization vector of the Mnlr anti-ferromagnetic layer are possible mechanisms of degradation. Furthermore, significant voiding caused by electromigration and thermal gradient induced atomic motion was observed at current densities higher than 35 MA/cm2. High-resolution temperature distribution measurements by scanning thermal probe microscopy revealed the existence of a huge temperature gradient of 106°C/cm, which is a strong driving force for atomic diffusion.

scholarly journals The effect of cobalt on morphology, structure, and ORR activity of electrospun carbon fibre mats in aqueous alkaline environments

2021 ◽  
Vol 12 ◽  
pp. 1173-1186
Author(s):  
Markus Gehring ◽  
Tobias Kutsch ◽  
Osmane Camara ◽  
Alexandre Merlen ◽  
Hermann Tempel ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Inductively Coupled Plasma ◽  
Elevated Temperatures ◽  
Current Collector ◽  
Alkaline Media ◽  
Emission Spectrometry ◽  
Free Standing ◽  
X Ray ◽  
Turbostratic Carbon ◽  
Current Densities

An innovative approach for the design of air electrodes for metal–air batteries are free-standing scaffolds made of electrospun polyacrylonitrile fibres. In this study, cobalt-decorated fibres are prepared, and the influence of carbonisation temperature on the resulting particle decoration, as well as on fibre structure and morphology is discussed. Scanning electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, and inductively coupled plasma optical emission spectrometry are used for characterisation. The modified fibre system is compared to a benchmark system without cobalt additives. Cobalt is known to catalyse the formation of graphite in carbonaceous materials at elevated temperatures. As a result of cobalt migration in the material the resulting overall morphology is that of turbostratic carbon. Nitrogen removal and nitrogen-type distribution are enhanced by the cobalt additives. At lower carbonisation temperatures cobalt is distributed over the surface of the fibres, whereas at high carbonisation temperatures it forms particles with diameters up to 300 nm. Free-standing, current-collector-free electrodes assembled from carbonised cobalt-decorated fibre mats display promising performance for the oxygen reduction reaction in aqueous alkaline media. High current densities at an overpotential of 100 mV and low overpotentials at current densities of 333 μA·cm−2 were found for all electrodes made from cobalt-decorated fibre mats carbonised at temperatures between 800 and 1000 °C.

scholarly journals Steady-state thermal gradient induced by pulsed laser excitation in a ferromagnetic layer

2016 ◽  
Vol 119 (15) ◽  
pp. 153904 ◽  
Author(s):  
S. Shihab ◽  
L. Thevenard ◽  
A. Lemaître ◽  
J.-Y. Duquesne ◽  
C. Gourdon
Keyword(s):  
Steady State ◽  
Thermal Gradient ◽  
Laser Excitation ◽  
Ferromagnetic Layer ◽  
Pulsed Laser

scholarly journals Critical switching characteristics of three-layered spin valve for different materials and alloys with uniaxial anisotropy

2018 ◽  
Vol 185 ◽  
pp. 01012
Author(s):  
Iuliia Iusipova
Keyword(s):  
Spin Valve ◽  
Uniaxial Anisotropy ◽  
Magnetization Vector ◽  
Time Switching ◽  
Magnetic Parameters ◽  
Ferromagnetic Layers ◽  
Cobalt Iron ◽  
Critical Characteristics ◽  
Switching Characteristics ◽  
Layered Spin

We analyze the dependence of the current density and magnetic field switching on the magnetic parameters of the material of the ferromagnetic layers of the spin valve. Comparison of critical characteristics of the spin valve with longitudinal anisotropy of ferromagnetic layers fabricared of different materials showed that the promising materials for the fabrication of spin valve are cobalt, iron, their alloys, ferroborates of cobalt and alloys of cobalt with gadolinium. For these materials we produced and analyzed the bifurcation diagrams of equations describing the switching process of the spin valve. Based on the study of the dynamics of the magnetization vector we obtained the numerical evaluation of time switching.

New Cathodic Protection Criteria Based on Direct and Alternating Current Densities Measured Using Coupons and Their Application to Modern Steel Pipelines

CORROSION ◽  
2004 ◽  
Vol 60 (3) ◽  
pp. 304-312 ◽  
Author(s):  
Y. Hosokawa ◽  
F. Kajiyama ◽  
Y. Nakamura
Keyword(s):  
Cathodic Protection ◽  
Field Tests ◽  
Alternating Current ◽  
Pipe Material ◽  
Review Of The Literature ◽  
Density Measurements ◽  
Corrosion Risk ◽  
Ac Current ◽  
Current Densities ◽  
Dc Current

Abstract The risks of alternating current (AC) corrosion, overprotection, and stray direct current (DC) corrosion are increasing on cathodically protected buried steel pipelines due to the recent changes in factors such as burial conditions, the characteristics of coatings, and pipe material. In the present study, field tests as well as a review of the literature on these risks were conducted. As a result, it has been revealed that there is a certain limitation to assess these risks with respect to conventional cathodic protection (CP) criteria based on pipe-to-soil potential. Therefore, new CP criteria for the elimination of these risks have been developed based on DC and AC current density measurements on coupons. The effectiveness of the new CP criteria was evaluated through the design of CP systems on newly constructed pipelines subject to the risks of AC corrosion, overprotection, and stray DC corrosion. Using these new CP criteria, the design and installation of CP systems as well as the elimination of these risks were completed successfully. The risks of overprotection as well as stray DC corrosion were eliminated by providing an appropriate level of DC current from CP rectifiers. The elimination of the AC corrosion risk was accomplished using distributed magnesium anodes and solid-state DC decoupling devices. Finally, the new CP criteria were proven to be effective in eliminating the risks of AC corrosion, overprotection, and stray DC corrosion on buried steel pipelines.

Layer selective determination of magnetization vector configurations in an epitaxial double spin valve structure: Si(001)/Cu/Co/Cu/FeNi/Cu/Co/Cu

2000 ◽  
Vol 77 (6) ◽  
pp. 892-894 ◽  
Author(s):  
B. C. Choi ◽  
A. Samad ◽  
C. A. F. Vaz ◽  
J. A. C. Bland ◽  
S. Langridge ◽  
...  
Keyword(s):  
Spin Valve ◽  
Magnetization Vector ◽  
Selective Determination ◽  
Double Spin ◽  
Valve Structure

GRAVITY AIDED TEXTURE GROWTH IN CERAMIC SUPERCONDUCTORS

1989 ◽  
Vol 03 (14) ◽  
pp. 1053-1060 ◽  
Author(s):  
A. J. BOURDILLON ◽  
N. X. TAN ◽  
N. SAVVIDES ◽  
J. SHARP
Keyword(s):  
Critical Current ◽  
Grain Growth ◽  
Thermal Gradient ◽  
Thermal Gradients ◽  
Ceramic Superconductor ◽  
Downward Motion ◽  
Ceramic Superconductors ◽  
Current Densities ◽  
Molten Phase

Texture growth in incongruently melting ceramic superconductor materials, such as YBa 2 Cu 3 O 7−x, can be combined with zone refinement in thermal gradients to increase critical current densities. In gravity aided texture growth (GATEG), a vertical thermal gradient is used with downward motion of the partially molten specimen (relative to the furnace) so that the molten phase recrystallizes with grain growth.

scholarly journals Частота и быстродействие спинового вентиля с планарной анизотропией слоев

2020 ◽  
Vol 62 (9) ◽  
pp. 1361
Author(s):  
Ю.А. Юсипова
Keyword(s):  
Spin Valve ◽  
Practical Interest ◽  
Magnetization Vector ◽  
Magnetization Dynamics ◽  
Operating Modes ◽  
Read Head ◽  
Ferromagnetic Layers ◽  
Valve Structure ◽  
Switching Characteristics ◽  
Layered Spin

The dynamics of the magnetization vector in the free layer of a layered spin-valve structure was simulated. As materials for the free and fixed layers, six magnetically soft ferromagnets with longitudinal anisotropy were considered. The types of magnetization dynamics that are of practical interest for MRAM and HMDD (switching of the magnetization vector), STNO (stable precession of the magnetization vector), and the base element PSL (switching of the magnetization vector with two probable outcomes) were highlighted. The ranges of currents and fields corresponding to these operating modes of the spin valve were calculated. The numerical calculations of the switching time showed that, among the considered materials for the MRAM cell, the most suitable is Co80Gd20 alloy, while for the HMDD read head, it is Fe60Co20B20. As a result of the precession frequency calculations, it was concluded that the Fe60Co20B20 alloy is optimal for the STNO ferromagnetic layers. For the implementation of PSL, the best switching characteristics were demonstrated by the Co93Gd7 alloy.

Stress-Induced Change of the Microstructure and Strength of Modified 9Cr-1Mo Steel Under Fatigue and Creep Loadings at Elevated Temperatures

2017 ◽  
Author(s):  
Taichi Shinozaki ◽  
Ken Suzuki ◽  
Hideo Miura
Keyword(s):  
Activation Energy ◽  
Applied Stress ◽  
Test Temperature ◽  
Elevated Temperatures ◽  
Critical Value ◽  
Atomic Diffusion ◽  
Dominant Factor ◽  
Martensitic Structure ◽  
Creep Tests ◽  
Microstructure Change

The change of the lath martensitic structure in modified 9Cr-1Mo steel was observed in the specimens after the fatigue and creep tests using EBSD (Electron Back-Scatter Diffraction). The Kernel Average Misorientation (KAM) value obtained from the EBSD analysis were used for the quantitative evaluation of the change in the lath martensitic texture. It was found that the average KAM values of the fractured specimens decreased clearly after 107−108 cycles of the fatigue loading at temperatures higher than 500°C when the amplitude of the applied stress exceeded a critical value. This change corresponded to the disappearance of the lath martensitic structure. The critical value decreased monotonically with the increase of the test temperature. This microstructure change decreased the strength of the alloy drastically. It was found that the change of the microstructure started at a certain time at each test temperature as a function of the amplitude of the applied stress. There was the critical stress at which the microstructure change started at each test temperature higher than 500°C, and the activation energy of the change was determined as a function of temperature and the amplitude of the applied stress. The dominant factor of the microstructure change was the stress-induced acceleration of the atomic diffusion of the component elements in the alloy. In order to improve the long-term reliability of the alloy, it is very important to increase the activation energy by modifying the microstructure of this alloy.

Suppressing atomic diffusion with the Schwarz crystal structure in supersaturated Al–Mg alloys

Science ◽  
2021 ◽  
Vol 373 (6555) ◽  
pp. 683-687
Author(s):  
W. Xu ◽  
B. Zhang ◽  
X. Y. Li ◽  
K. Lu
Keyword(s):  
Crystal Structure ◽  
Elevated Temperatures ◽  
Atomic Diffusion ◽  
Structure And Properties ◽  
Equilibrium Melting Temperature ◽  
Diffusion Controlled ◽  
Engineering Alloys ◽  
Al Mg Alloys ◽  
Stable Structures ◽  
Boundary Diffusivity

High atomic diffusivity in metals enables substantial tuneability of their structure and properties by tailoring the diffusional processes, but this causes their customized properties to be unstable at elevated temperatures. Eliminating diffusive interfaces by fabricating single crystals or heavily alloying helps to address this issue but does not inhibit atomic diffusion at high homologous temperatures. We discovered that the Schwarz crystal structure was effective at suppressing atomic diffusion in a supersaturated aluminum–magnesium alloy with extremely fine grains. By forming these stable structures, diffusion-controlled intermetallic precipitation from the nanosized grains and their coarsening were inhibited up to the equilibrium melting temperature, around which the apparent across-boundary diffusivity was reduced by about seven orders of magnitude. Developing advanced engineering alloys using the Schwarz crystal structure may lead to useful properties for high-temperature applications.

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