Antisite defects versus grain boundary competition in the tunneling magnetoresistance of theSr2FeMoO6double perovskite

2004 ◽  
Vol 70 (13) ◽  
Author(s):  
D. Niebieskikwiat ◽  
F. Prado ◽  
A. Caneiro ◽  
R. D. Sánchez
Keyword(s):  
Grain Boundary ◽  
Tunneling Magnetoresistance ◽  
Antisite Defects

scholarly journals Laser Microscopy of Tunneling Magnetoresistance in Manganite Grain-Boundary Junctions

2006 ◽  
Vol 96 (4) ◽  
Author(s):  
M. Wagenknecht ◽  
H. Eitel ◽  
T. Nachtrab ◽  
J. B. Philipp ◽  
R. Gross ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Tunneling Magnetoresistance ◽  
Laser Microscopy

scholarly journals Atomistic Studies of Grain Boundaries in NiAl

1994 ◽  
Vol 364 ◽  
Author(s):  
M. Yan ◽  
S. P. Chen ◽  
V. Vitek
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Cohesive Strength ◽  
Antisite Defects

AbstractThis paper presents the results of atomistic studies of grain boundaries in NiAl B2 alloy. The interatomic forces are described by Finnis-Sinclair type N-body potentials, and are fitted to properties of NiAl. The results show that the structure, energy and cohesive strength of a grain boundary depend strongly on its chemistry, and a grain boundary possessing more Al is the weakest. Energies of antisite defects at the grain boundary ∑5 {210} are also calculated, and the results suggest that Al has much larger tendency to segregate at a grain boundary than Ni does.

Preparation and characteristics of 90° rotated biepitaxial Fe3O4 thin films

2002 ◽  
Vol 17 (8) ◽  
pp. 1985-1991 ◽  
Author(s):  
Hiroshi Matsuda ◽  
Hiroshi Sakakima ◽  
Hideaki Adachi ◽  
Akihiro Odagawa ◽  
Kentaro Setsune
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Magnetic Properties ◽  
Electron Diffraction ◽  
Grain Boundary ◽  
Seed Layer ◽  
Tunneling Magnetoresistance ◽  
X Ray ◽  
Transmission Electron

In-plane 90° rotated biepitaxial Fe3O4 thin films have been successfully prepared onto MgO (110) substrates using a CeO2 seed layer and their microstructure, electric, and magnetic properties were investigated. From the x-ray φ-scan measurements, the in-plane epitaxial relations were determined as 〈110〉Fe3O4//〈110〉MgO and 〈001〉Fe3O4//〈001〉MgO for the no-seeded Fe3O4 layer, and 〈001〉Fe3O4//〈110〉MgO and 〈110〉Fe3O4//〈001〉MgO for the CeO2 (110) seeded Fe3O4 layer. The CeO2 seed layer was found to rotate the upper Fe3O4 lattice at 90° upon normal axis to the layer against the no-seeded Fe3O4. The transmission electron microscopy and electron diffraction analyses revealed that the transition region of the biepitaxial Fe3O4 boundary between CeO2-seeded and no-seeded portions consisted of columnarlike polycrystalline grains. The Fe 3O4 films exhibited single-crystallinelike electric and magnetic properties, however, substantial spin-dependent-tunneling magnetoresistance across the 90° grain boundary was not observed even in the antiparallel situation for each Fe3O4 portion.

The Competitive and Combining Effects of Grain Boundary and Fe/Mo Antisite Defects on the Low-Field Magnetoresistance in Sr2 FeMoO6

2013 ◽  
Vol 97 (4) ◽  
pp. 1137-1142 ◽  
Author(s):  
Jin-Feng Wang ◽  
Zheng Li ◽  
Xi-Jun Xu ◽  
Zheng-Bin Gu ◽  
Guo-Liang Yuan ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Low Field ◽  
Antisite Defects

Structure of the Σ=5 (310) interface in NiAl

1993 ◽  
Vol 51 ◽  
pp. 984-985
Author(s):  
Richard W. Fonda ◽  
David E. Luzzi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Point Defects ◽  
Low Temperatures ◽  
High Resolution Electron Microscopy ◽  
Image Simulation ◽  
Embedded Atom ◽  
Resolution Electron ◽  
Antisite Defects ◽  
Simulated Images

The atomic structure of the Σ=5 [001] (310) grain boundary in NiAl was examined by high resolution electron microscopy and multislice image simulation. As in most other intermetallic compounds, the grain boundaries in NiAl are intrinsically brittle at low temperatures. Although there have been few studies on this alloy, the energies of NiAl grain boundaries have been calculated using embedded atom potentials for both stoichiometric and non-stoichiometric structures. These studies are consistent with the results of Bradley and Taylor, which indicate that nickel-rich compositions result from nickel antisite defects on the aluminum sublattice, while aluminum-rich compositions produce constitutional vacancies on the nickel sublattice, and with recent field ion microscopy results on nickel-rich alloys.The Σ=5 grain boundary was prepared by diffusion bonding at 1000 °C. A JEOL 4000EX was used for HREM imaging and the NUMIS multislice simulation program was used to simulated images. Analysis of these images considered the effects of grain boundary expansion, rigid body displacements along the boundary, grain boundary stoichiometry, and point defects at the boundary.

scholarly journals Voltage and temperature dependence of the grain boundary tunneling magnetoresistance in manganites

2000 ◽  
Vol 50 (5) ◽  
pp. 681-687 ◽  
Author(s):  
C Höfener ◽  
J. B Philipp ◽  
J Klein ◽  
L Alff ◽  
A Marx ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Temperature Dependence ◽  
Tunneling Magnetoresistance

Dependence of Intergranular Fracture on Boundary Topography and Cohesion

1973 ◽  
Vol 31 ◽  
pp. 150-151
Author(s):  
J. E. Doherty ◽  
A. F. Giamei ◽  
B. H. Kear ◽  
C. W. Steinke
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Nickel Base Superalloy ◽  
Boundary Shear ◽  
Room Temperature Ductility ◽  
Solid Solution Matrix ◽  
Nickel Base ◽  
Solution Matrix ◽  
Different Levels ◽  
Base Superalloy

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.

Two Investigations into Grain Boundary Structure

1977 ◽  
Vol 35 ◽  
pp. 688-691
Author(s):  
P. Humble
Keyword(s):  
Grain Boundary ◽  
Dark Field ◽  
Boundary Structure ◽  
Boundary Dislocation ◽  
Bright Field ◽  
Intrinsic Structure ◽  
Weak Beam ◽  
Grain Boundary Structure ◽  
Independent Information ◽  
Diffraction Patterns

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.

Metallurgical Effects of Grain Boundary Ledges

1977 ◽  
Vol 35 ◽  
pp. 126-129
Author(s):  
L.E. Murr
Keyword(s):  
Grain Boundary ◽  
Quantitative Data ◽  
Mechanical Treatment ◽  
Unit Length ◽  
Physical And Mechanical Properties ◽  
Direct Observations ◽  
Transmission Electron ◽  
Properties Of Materials ◽  
Thermo Mechanical Treatment ◽  
Ledge Density

Ledges in grain boundaries can be identified by their characteristic contrast features (straight, black-white lines) distinct from those of lattice dislocations, for example1,2 [see Fig. 1(a) and (b)]. Simple contrast rules as pointed out by Murr and Venkatesh2, can be established so that ledges may be recognized with come confidence, and the number of ledges per unit length of grain boundary (referred to as the ledge density, m) measured by direct observations in the transmission electron microscope. Such measurements can then give rise to quantitative data which can be used to provide evidence for the influence of ledges on the physical and mechanical properties of materials.It has been shown that ledge density can be systematically altered in some metals by thermo-mechanical treatment3,4.

Measurement of the Displacement Across a Coincidence Grain Boundary

1977 ◽  
Vol 35 ◽  
pp. 124-125
Author(s):  
J. W. Matthews ◽  
W. M. Stobbs
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Stacking Fault ◽  
The Other ◽  
Measuring Technique ◽  
High Angle ◽  
Twin Boundaries ◽  
Rigid Displacement ◽  
Cubic Crystals ◽  
Lattice Displacement

Many high-angle grain boundaries in cubic crystals are thought to be either coincidence boundaries (1) or coincidence boundaries to which grain boundary dislocations have been added (1,2). Calculations of the arrangement of atoms inside coincidence boundaries suggest that the coincidence lattice will usually not be continuous across a coincidence boundary (3). There will usually be a rigid displacement of the lattice on one side of the boundary relative to that on the other. This displacement gives rise to a stacking fault in the coincidence lattice.Recently, Pond (4) and Smith (5) have measured the lattice displacement at coincidence boundaries in aluminum. We have developed (6) an alternative to the measuring technique used by them, and have used it to find two of the three components of the displacement at {112} lateral twin boundaries in gold. This paper describes our method and presents a brief account of the results we have obtained.

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