scholarly journals Dynamic in situ observation of voltage-driven repeatable magnetization reversal at room temperature

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Ya Gao ◽  
Jia-Mian Hu ◽  
C. T. Nelson ◽  
T. N. Yang ◽  
Y. Shen ◽  
...  
Keyword(s):  
Magnetization Reversal ◽  
Room Temperature ◽  
In Situ Observation

In situ TEM study of irradiation-induced transformation in TiNi shape memory alloys

2003 ◽  
Vol 792 ◽  
Author(s):  
X. T. Zu ◽  
F.R. Wan ◽  
S. Zhu ◽  
L. M. Wang
Keyword(s):  
Phase Transformation ◽  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Electron Irradiation ◽  
Room Temperature ◽  
Critical Voltage ◽  
In Situ Tem ◽  
In Situ Observation

ABSTRACTTiNi shape memory alloy (SMA) has potential applications for nuclear reactors and its phase stability under irradiation is becoming an important topic. Some irradiation-induced diffusion-dependent phase transformations, such as amorphization, have been reported before. In the present work, the behavior of diffusion-independent phase transformation in TiNi SMA was studied by electron irradiation at room temperature. The effect of irradiation on the martensitic transformation of TiNi shape memory alloys was studied by Transmission Electron Microscopy (TEM) with in-situ observation and differential scanning calorimeter (DSC). The results of TEM and DSC measurements show that the microstructure of samples is R phase at room temperature. Electron irradiations were carried out using several different TEM with accelerating voltage of 200 kV, 300 kV, 400 kV and 1000 kV. Also the accelerating voltage in the same TEM was changed to investigate the critical voltage for the effect of irradiation on phase transformation. It was found that a phase transformation occurred under electron irradiation above 320 kV, but never appeared at 300 kV or lower accelerating voltage. Such phase transformation took place in a few seconds of irradiation and was independent of atom diffusion. The mechanism of Electron-irradiation-induced the martensitic transformation due to displacements of atoms from their lattice sites produced by the accelerated electrons.

Crystallographic Features of the A-Type and CE-Type Antiferromagnetic States in the Simple-Perovskite Manganite System Sr1-xNdxMnO3

2011 ◽  
Vol 409 ◽  
pp. 532-537
Author(s):  
Yusuke Onezawa ◽  
Yasuhide Inoue ◽  
Masazumi Arao ◽  
Yasumasa Koyama
Keyword(s):  
Room Temperature ◽  
Three Dimensional ◽  
Electronic System ◽  
Paramagnetic State ◽  
Heating Process ◽  
In Situ Observation ◽  
Perovskite Manganite ◽  
Transmission Electron ◽  
Highly Correlated

The electronic states of Sr1-xNdxMnO3 with the simple perovskite structure are characterized by a three-dimensional highly-correlated electronic system. To understand the detailed features of the A-and CE-type antiferromagnetic states in this system, their crystallographic features for x = 0.47, 0.48, and 0.50 have been investigated mainly by both x-ray powder diffraction and transmission electron microscopy. It was found at room temperature that the crystal structure for x = 0.47 was determined to have the monoclinic C2/m symmetry, while the orthorhombic Imma structure was confirmed for x = 0.48 and 0.50. The in-situ observation for x = 0.47 indicated that, in the heating process from room temperature, the C2/m-to-Imma transition occurred in the paramagnetic state, and that the A-type antiferromagnetic state appeared below about 200 K on cooling. In addition, the cooling from room temperature for x = 0.48 and 0.50 resulted in the direct transitions from the orthorhombic Imma state to the A-and CE-type antiferromagnetic states, respectively. Based on these features, we simply discussed the physical origin of the appearance of the paramagnetic state with the monoclinic symmetry for x = 0.47.

Structural and Optical Properties of β-FeSi2/Si(100) Prepared by Laser Ablation Method

1997 ◽  
Vol 478 ◽  
Author(s):  
H. Kakemoto ◽  
Y. Makita ◽  
A. Obara ◽  
Y. Tsai ◽  
S. Sakuragi ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Room Temperature ◽  
Horizontal Gradient ◽  
In Situ Observation ◽  
X Ray Diffraction ◽  
Energy Devices ◽  
Laser Ablation Method ◽  
Semiconducting Properties ◽  
Morphology Characterization

Abstractβ-FeSi2 is a promising material for the application of various electronic, optoelectronic and energy devices. We present here the semiconducting properties of β-FeSi2 films on Si(100) substrate prepared by laser ablation method. Samples were grown using poly-crystalline bulk β-FeSi2 prepared by horizontal gradient freeze method. For the monitoring of growth, in-situ observation of ablation plume was made through fluorescence spectroscopy. Reflection of highenergy electron beam diffraction (RHEED) was also made in-situ to see the surface morphology. Characterization of the films by X-ray diffraction presented purely P3(220) orientation. Raman scattering measurements at room temperature also indicated that the grown films are semiconducting β-FeSi2. Optical absorption spectra at room temperature showed absorption coefficient higher than 105 cm−1 above the band-gap (˜1.2 eV). It was revealed that high quality semiconducting β-FeSi2 films can be fabricated by laser ablation method without post-annealing.

In-situ observation of magnetization reversal process of Sm(Co,Cu,Fe,Zr)z magnets with different Fe contents

Rare Metals ◽  
2019 ◽  
Vol 39 (3) ◽  
pp. 250-255 ◽  
Author(s):  
Shuo Wu ◽  
Dong-Tao Zhang ◽  
Ming Yue ◽  
Yun-Qiao Wang ◽  
Zhi-Feng Shang ◽  
...  
Keyword(s):  
Magnetization Reversal ◽  
In Situ Observation ◽  
Reversal Process ◽  
Magnetization Reversal Process

In-Situ Observation of Transition Between Surface Relief and Wrinkling in Thin Film Shape Memory Alloys

2008 ◽  
Vol 8 (5) ◽  
pp. 2588-2596 ◽  
Author(s):  
Y. Q. Fu ◽  
S. Sanjabi ◽  
Z. H. Barber ◽  
W. M. Huang ◽  
M. Cai ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Surface Relief ◽  
Room Temperature ◽  
Critical Dimension ◽  
In Situ Observation ◽  
Morphology Evolution ◽  
Surface Wrinkling ◽  
Sputter Deposited ◽  
Surface Morphology Evolution

Significant surface morphology evolution between relief and wrinkling was observed on a 3.5 μm thick TiNiCu film sputter-deposited on a silicon substrate. At room temperature, variation in surface relief morphology (from separated martensite crystals embedded in amorphous matrix to fully inter-weaved martensite plates) was observed with slight change in film composition. The phenomenon was attributed to variations in crystallization temperatures of as-deposited amorphous films during annealing because of the compositional difference. During thermal cycling between room temperature and 100 °C, reversible surface morphology changes can be observed between surface relief and wrinkling patterns. The formation of the surface wrinkling is attributed to the large compressive stress in the film during high temperature post-annealing and crystallization, whereas surface relief is caused by the martensitic transformation to relieve the large tensile stress in the film. Compositional effect on this surface morphology evolution is discussed. Results also indicate that there is a critical dimension for the wrinkling to occur, and a small circular island can only relax by in-plane expansion.

In Situ Observation of Nanocrystal Formation Via Dehydroxylation

2001 ◽  
Vol 7 (S2) ◽  
pp. 438-439
Author(s):  
Renu Sharma ◽  
M. J. McKelvy ◽  
Hamdallah Bearat ◽  
Andrew V.G. Chizmeshya ◽  
R.W. Carpenter
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
High Vacuum ◽  
Atomic Level ◽  
Metal Particles ◽  
In Situ Observation ◽  
Fine Powders ◽  
Environmental Cell ◽  
Nanocrystal Formation

Recently, a promising new route to prepare nano phase composites with fine transition metal particles (2 - 50nm) has been proposed via dehydroxylation and dehydration process. Thermal and mechanical dehydroxylation process has also been used to form ultra fine powders of NiO-Ni(OH). We have found a substantially increased carbonation rate at room temperature (RT) for partially dehydroxylated brucite (Mg(OH)2) single crystal fragments. BET measurements confirm the increase in the surface area of partially dehydroxylated (90%) single-crystal Mg(OH)2 fragments, which directly contributes to the increase in carbonation reactivity. As dehydroxylation proceeds rapidly in a TEM column, due to high vacuum and electron beam effects, the atomic level nature of the process has not been understood until recently.6 We have observed the development of nanocrystals during in situdehydroxylation of Mg(OH)2.Experiments were performed using a PHILIPS-430 electron microscope operated at 300KV, fitted with a differentially pumped environmental-cell (E-cell) and a Gatan Imaging Filter (GIF).

In-Situ Observation of Deformation Associated with R-Phase in NiTi Shape Memory Alloy

1995 ◽  
Vol 404 ◽  
Author(s):  
Y. Gao ◽  
Y. Q. Liu ◽  
K. H. Wu
Keyword(s):  
Martensite Transformation ◽  
Room Temperature ◽  
Strain Curve ◽  
Deformation Mode ◽  
Niti Shape Memory Alloy ◽  
In Situ Observation ◽  
Stress Strain Curve ◽  
Second Stage ◽  
Transmission Electron

AbstractAn in-situ straining experiment was performed in a transmission electron microscope (TEM) on the polycrystalline Ti49Ni51 alloy with full R-phase at room temperature. The reorientation of Rphase variants to a single, favorable one was observed under small stress at the beginning of straining, corresponding to the deformation mode of the first yielding stage. During further straining, the observation showed that the reoriented R-phase undergoes a stress-induced martensite transformation, and this dynamic process was considered to contribute to the second stage deformation in the R-phase stress-strain curve. The orientation relationship between the R-phase and stress-induced martensite has been determined and the internal (001)M twins were found in the stressinduced martensite plates.

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