Energy barriers for bit-encoding states based on 360° domain walls in ultrathin ferromagnetic nanorings

2015 ◽  
Vol 117 (17) ◽  
pp. 17D118 ◽  
Author(s):  
C. B. Muratov ◽  
V. V. Osipov ◽  
E. Vanden-Eijnden
Keyword(s):  
Domain Walls ◽  
Energy Barriers ◽  
Ferromagnetic Nanorings

scholarly journals The creation of 360° domain walls in ferromagnetic nanorings by circular applied magnetic fields

2014 ◽  
Vol 115 (17) ◽  
pp. 17D135 ◽  
Author(s):  
Jessica E. Bickel ◽  
Spencer A. Smith ◽  
Katherine E. Aidala
Keyword(s):  
Magnetic Fields ◽  
Domain Walls ◽  
The Creation ◽  
Ferromagnetic Nanorings

scholarly journals Local and global energy barriers for chiral domain walls in synthetic antiferromagnet-ferromagnet lateral junctions

2021 ◽  
Author(s):  
Jiho Yoon ◽  
See-Hun Yang ◽  
Jae-Chun Jeon ◽  
Andrea Migliorini ◽  
Ilya Kostanovskiy ◽  
...  
Keyword(s):  
Small Volume ◽  
Domain Walls ◽  
High Reliability ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Energy Barriers ◽  
Trade Off ◽  
Synthetic Antiferromagnet ◽  
Fundamental Research ◽  
Low Threshold

Abstract The current induced manipulation of chiral spin textures is of great interest for both fundamental research and technological applications1–3. Of particular interest are magnetic non-volatile memories formed from synthetic antiferromagnetic racetracks in which chiral composite domain walls (DWs), that act as data bits, can be efficiently moved by current4. However, overcoming the trade-off between energy efficiency, namely a low threshold current density to move the domain walls, and high thermal stability, remains a major challenge for the development of integrated chips with high reliability and low power consumption. Here we show that chiral DWs5–7 in a synthetic antiferromagnet-ferromagnet lateral junction, formed by local plasma oxidation, are highly stable against large magnetic fields whilst the DWs can be efficiently moved across the junction by current. Our approach takes advantage of the locality of current-driven torque on the small volume of a chiral DW and the globality of field-torque in the energy landscape, thereby leading to fundamentally distinct energy barriers for motion and stability. We find that the threshold current can be further decreased by tilting the junction across the racetrack while not affecting the high DW stability. Furthermore, we demonstrate that chiral DWs can be robustly confined within a ferromagnet region sandwiched on both their sides by synthetic antiferromagnets and yet can be readily injected into these regions by current. Our findings break the aforementioned trade-off between efficiency and stability, allowing for diverse and versatile DW-based memory, and logic, and beyond.

scholarly journals Stability of $2\pi$ Domain Walls in Ferromagnetic Nanorings

2010 ◽  
Vol 46 (6) ◽  
pp. 2272-2274 ◽  
Author(s):  
Gabriel D. Chaves-O'Flynn ◽  
Daniel Bedau ◽  
Eric Vanden-Eijnden ◽  
Andrew D. Kent ◽  
Daniel L. Stein
Keyword(s):  
Domain Walls ◽  
Ferromagnetic Nanorings

scholarly journals Magnetization Reversal in Ferromagnetic Nanorings of Fourfold Symmetries

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Andrea Ehrmann ◽  
Tomasz Blachowicz
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetization Reversal ◽  
Domain Walls ◽  
Memory Devices ◽  
Micromagnetic Simulations ◽  
Stable Intermediate ◽  
Intermediate States ◽  
The Stability ◽  
Ferromagnetic Nanorings

Magnetic nanoparticles offer a broad spectrum of magnetization reversal processes and respective magnetic states, such as onion, horseshoe, or vortex states as well as various states including domain walls. These states can be correlated with stable intermediate states at remanence, enabling new quaternary memory devices storing two bits in one particle. The stability of these intermediated states was tested with respect to shape modifications, variations in the anisotropy axes, and rotations and fluctuations of the external magnetic field. In our micromagnetic simulations, 6 different stable intermediate states were observed at vanishing magnetic field in addition to the remanence state. The angular region of approx. 5°–12° between nanoring and external magnetic field was identified as being most stable with respect to all modifications, with an onion state as technologically best accessible intermediate state to create quaternary memory devices.

The direct determination of magnetic domain wall profiles using a split detector STEM

1978 ◽  
Vol 36 (1) ◽  
pp. 466-467
Author(s):  
J.N. Chapman ◽  
P.E. Batson ◽  
E.M. Waddell ◽  
R.P. Ferrier
Keyword(s):  
Electron Microscope ◽  
Domain Wall ◽  
Transmission Electron Microscope ◽  
Domain Walls ◽  
Photographic Plate ◽  
Magnetic Domain ◽  
Direct Determination ◽  
Quantitative Information ◽  
Scanning Transmission Electron Microscope ◽  
Transmission Electron

By far the most commonly used mode of Lorentz microscopy in the examination of ferromagnetic thin films is the Fresnel or defocus mode. Use of this mode in the conventional transmission electron microscope (CTEM) is straightforward and immediately reveals the existence of all domain walls present. However, if such quantitative information as the domain wall profile is required, the technique suffers from several disadvantages. These include the inability to directly observe fine image detail on the viewing screen because of the stringent illumination coherence requirements, the difficulty of accurately translating part of a photographic plate into quantitative electron intensity data, and, perhaps most severe, the difficulty of interpreting this data. One solution to the first-named problem is to use a CTEM equipped with a field emission gun (FEG) (Inoue, Harada and Yamamoto 1977) whilst a second is to use the equivalent mode of image formation in a scanning transmission electron microscope (STEM) (Chapman, Batson, Waddell, Ferrier and Craven 1977), a technique which largely overcomes the second-named problem as well.

Lorentz microscopy study of magnetic domain walls in Fe-Cr-Co alloys

1978 ◽  
Vol 36 (1) ◽  
pp. 462-463
Author(s):  
Yalcin Belli
Keyword(s):  
Domain Walls ◽  
Magnetic Domain ◽  
Microscopy Study ◽  
Ferromagnetic Phase ◽  
Stable Phase ◽  
Magnetic Domains ◽  
Lorentz Microscopy ◽  
Magnetic Hardening ◽  
Electron Microscopes ◽  
Co Alloys

Fe-Cr-Co alloys have great technological potential to replace Alnico alloys as hard magnets. The relationship between the microstructures and the magnetic properties has been recently established for some of these alloys. The magnetic hardening has been attributed to the decomposition of the high temperature stable phase (α) into an elongated Fe-rich ferromagnetic phase (α1) and a weakly magnetic or non-magnetic Cr-rich phase (α2). The relationships between magnetic domains and domain walls and these different phases are yet to be understood. The TEM has been used to ascertain the mechanism of magnetic hardening for the first time in these alloys. The present paper describes the magnetic domain structure and the magnetization reversal processes in some of these multiphase materials. Microstructures to change properties resulting from, (i) isothermal aging, (ii) thermomagnetic treatment (TMT) and (iii) TMT + stepaging have been chosen for this investigation. The Jem-7A and Philips EM-301 transmission electron microscopes operating at 100 kV have been used for the Lorentz microscopy study of the magnetic domains and their interactions with the finely dispersed precipitate phases.

Temperature Dependence of Magnetic Domains and Wall Structures

1972 ◽  
Vol 30 ◽  
pp. 496-497
Author(s):  
Sonoko Tsukahara ◽  
Tadami Taoka ◽  
Hisao Nishizawa
Keyword(s):  
Temperature Dependence ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Iron Film ◽  
Objective Lens ◽  
Lorentz Microscopy ◽  
Domain Structures ◽  
Wall Structures ◽  
Crystal Films ◽  
Metallurgical Structure

The high voltage Lorentz microscopy was successfully used to observe changes with temperature; of domain structures and metallurgical structures in an iron film set on the hot stage combined with a goniometer. The microscope used was the JEM-1000 EM which was operated with the objective lens current cut off to eliminate the magnetic field in the specimen position. Single crystal films with an (001) plane were prepared by the epitaxial growth of evaporated iron on a cleaved (001) plane of a rocksalt substrate. They had a uniform thickness from 1000 to 7000 Å.The figure shows the temperature dependence of magnetic domain structure with its corresponding deflection pattern and metallurgical structure observed in a 4500 Å iron film. In general, with increase of temperature, the straight domain walls decrease in their width (at 400°C), curve in an iregular shape (600°C) and then vanish (790°C). The ripple structures with cross-tie walls are observed below the Curie temperature.

Imaging of ferroelectric domain walls by electron holography

1992 ◽  
Vol 50 (1) ◽  
pp. 246-247
Author(s):  
Xiao Zhang
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Domain Walls ◽  
Ferroelectric Domain ◽  
Object Wave ◽  
Electron Holography ◽  
High Resolution Imaging ◽  
Quantitative Measurements ◽  
Resolution Imaging ◽  
Electron Microscopes

Electron holography has recently been available to modern electron microscopy labs with the development of field emission electron microscopes. The unique advantage of recording both amplitude and phase of the object wave makes electron holography a effective tool to study electron optical phase objects. The visibility of the phase shifts of the object wave makes it possible to directly image the distributions of an electric or a magnetic field at high resolution. This work presents preliminary results of first high resolution imaging of ferroelectric domain walls by electron holography in BaTiO3 and quantitative measurements of electrostatic field distribution across domain walls.

The need of electron microscopy in the study of domains and domain walls in ferroelectrics

1994 ◽  
Vol 52 ◽  
pp. 550-551
Author(s):  
Wenwu Cao
Keyword(s):  
Domain Wall ◽  
Domain Walls ◽  
High Mobility ◽  
Continuum Theory ◽  
Polarization Vector ◽  
Ferroelectric Materials ◽  
Dielectric Constants ◽  
Nonlocal Coupling ◽  
Cubic Symmetry ◽  
Gradient Energy

Domain structures play a key role in determining the physical properties of ferroelectric materials. The formation of these ferroelectric domains and domain walls are determined by the intrinsic nonlinearity and the nonlocal coupling of the polarization. Analogous to soliton excitations, domain walls can have high mobility when the domain wall energy is high. The domain wall can be describes by a continuum theory owning to the long range nature of the dipole-dipole interactions in ferroelectrics. The simplest form for the Landau energy is the so called ϕ model which can be used to describe a second order phase transition from a cubic prototype,where Pi (i =1, 2, 3) are the components of polarization vector, α's are the linear and nonlinear dielectric constants. In order to take into account the nonlocal coupling, a gradient energy should be included, for cubic symmetry the gradient energy is given by,

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