scholarly journals Asymmetric Magnetization Reversal in Exchange-Biased Hysteresis Loops

2000 ◽  
Vol 84 (17) ◽  
pp. 3986-3989 ◽  
Author(s):  
M. R. Fitzsimmons ◽  
P. Yashar ◽  
C. Leighton ◽  
Ivan K. Schuller ◽  
J. Nogués ◽  
...  
Keyword(s):  
Magnetization Reversal ◽  
Hysteresis Loops

scholarly journals Micromagnetic Simulations of Fe and Ni Nanodot Arrays Surrounded by Magnetic or Non-Magnetic Matrices

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 349
Author(s):  
Devika Sudsom ◽  
Andrea Ehrmann
Keyword(s):  
Magnetic Materials ◽  
Data Storage ◽  
Magnetization Reversal ◽  
Hysteresis Loops ◽  
Object Oriented ◽  
Basic Research ◽  
Memory Systems ◽  
The Other ◽  
Micromagnetic Simulations ◽  
Nanodot Arrays

Combining clusters of magnetic materials with a matrix of other magnetic materials is very interesting for basic research because new, possibly technologically applicable magnetic properties or magnetization reversal processes may be found. Here we report on different arrays combining iron and nickel, for example, by surrounding circular nanodots of one material with a matrix of the other or by combining iron and nickel nanodots in air. Micromagnetic simulations were performed using the OOMMF (Object Oriented MicroMagnetic Framework). Our results show that magnetization reversal processes are strongly influenced by neighboring nanodots and the magnetic matrix by which the nanodots are surrounded, respectively, which becomes macroscopically visible by several steps along the slopes of the hysteresis loops. Such material combinations allow for preparing quaternary memory systems, and are thus highly relevant for applications in data storage and processing.

scholarly journals Study of the influence of conditions of synthesis on magnetic characteristics of composite materials based on iron powders

2020 ◽  
Vol 65 (1) ◽  
pp. 17-24
Author(s):  
A. K. Vetcher ◽  
G. A. Govor ◽  
K. I. Yanushkevich ◽  
U. T. Berdiev ◽  
F. F. Khasanov
Keyword(s):  
Composite Materials ◽  
Magnetization Reversal ◽  
Metallic Iron ◽  
Low Frequency ◽  
Hysteresis Loops ◽  
Inert Atmosphere ◽  
Magnetic Characteristics ◽  
Pressing Method ◽  
Iron Powders ◽  
Synthesis Conditions

The influence of synthesis conditions on the magnetic characteristics of composite materials based on iron powders ASC 100.29 (Sweden) and LiaoNing (China) is investigated. The surface of metallic iron powders is encapsulated by an insulating ferrite coating, consisting of iron oxides and phosphides. The synthesis was carried out at a temperature of 150 °C from a gaseous medium in a special reactor at a pressure of 1 atm. Insulating oxide coatings were applied both to the initial iron powder without treatment, and to previously annealed powders in an inert atmosphere and in a mixture of hydrogen-argon. To conduct studies of magnetic characteristics, cores in the form of rings were made by pressing method. The dependence of induction vs. magnitude of the magnetic field, magnetization reversal losses (hysteresis losses) in the full and in the private loop were recorded by an express magnetometer. The value of losses was calculated by the hysteresis loops area. The results show that composite low-frequency magnetic materials based on metallic iron ASC 100.29 and LiaoNing powders have similar values of magnetic parameters – almost identical B = f(H) dependencies, but the magnetization reversal losses for ASC 100.29 are significantly lower than for LiaoNing powder under equal insulating coatings synthesis conditions. It is possible to use such materials as magnetic cores in various electrical devices, such as cores of high-frequency transformers and a number of electrical machines. Since such materials can operate at frequencies from 1 kHz and higher, this will significantly reduce the overall dimensions and increase the efficiency of electrical products.

scholarly journals Asymmetric Hysteresis Loops in Structured Ferromagnetic Nanoparticles with Hard/Soft Areas

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 800
Author(s):  
Joscha Detzmeier ◽  
Kevin Königer ◽  
Tomasz Blachowicz ◽  
Andrea Ehrmann
Keyword(s):  
Magnetization Reversal ◽  
Thermal Effects ◽  
Hysteresis Loops ◽  
Ferromagnetic Nanoparticles ◽  
Zero Temperature ◽  
Small Deviations ◽  
Micromagnetic Simulations ◽  
Random Anisotropy ◽  
Ferromagnetic Nanostructures ◽  
Biased Samples

Horizontally shifted and asymmetric hysteresis loops are often associated with exchange-biased samples, consisting of a ferromagnet exchange coupled with an antiferromagnet. In purely ferromagnetic samples, such effects can occur due to undetected minor loops or thermal effects. Simulations of ferromagnetic nanostructures at zero temperature with sufficiently large saturation fields should not lead to such asymmetries. Here we report on micromagnetic simulations at zero temperature, performed on sputtered nanoparticles with different structures. The small deviations of the systems due to random anisotropy orientations in the different grains can not only result in strong deviations of magnetization reversal processes and hysteresis loops, but also lead to distinctly asymmetric, horizontally shifted hysteresis loops in purely ferromagnetic nanoparticles.

scholarly journals Magnetization Reversal Process and Magnetostatic Interactions in Fe56Co44/SiO2/Fe3O4 Core/Shell Ferromagnetic Nanowires with Non-Magnetic Interlayer

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2282
Author(s):  
Javier García ◽  
Alejandro M. Manterola ◽  
Miguel Méndez ◽  
Jose Angel Fernández-Roldán ◽  
Víctor Vega ◽  
...  
Keyword(s):  
Data Storage ◽  
Magnetization Reversal ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Hysteresis Loops ◽  
Magnetic Data ◽  
Core Shell ◽  
The Core ◽  
Shell Nanostructures ◽  
Magnetostatic Interactions

Nowadays, numerous works regarding nanowires or nanotubes are being published, studying different combinations of materials or geometries with single or multiple layers. However, works, where both nanotube and nanowires are forming complex structures, are scarcer due to the underlying difficulties that their fabrication and characterization entail. Among the specific applications for these nanostructures that can be used in sensing or high-density magnetic data storage devices, there are the fields of photonics or spintronics. To achieve further improvements in these research fields, a complete understanding of the magnetic properties exhibited by these nanostructures is needed, including their magnetization reversal processes and control of the magnetic domain walls. In order to gain a deeper insight into this topic, complex systems are being fabricated by altering their dimensions or composition. In this work, a successful process flow for the additive fabrication of core/shell nanowires arrays is developed. The core/shell nanostructures fabricated here consist of a magnetic nanowire nucleus (Fe56Co44), grown by electrodeposition and coated by a non-magnetic SiO2 layer coaxially surrounded by a magnetic Fe3O4 nanotubular coating both fabricated by means of the Atomic Layer Deposition (ALD) technique. Moreover, the magnetization reversal processes of these coaxial nanostructures and the magnetostatic interactions between the two magnetic components are investigated by means of standard magnetometry and First Order Reversal Curve methodology. From this study, a two-step magnetization reversal of the core/shell bimagnetic nanostructure is inferred, which is also corroborated by the hysteresis loops of individual core/shell nanostructures measured by Kerr effect-based magnetometer.

Micromagnetic simulation study of magnetization reversal in torus-shaped permalloy nanorings

2017 ◽  
Vol 31 (22) ◽  
pp. 1750162 ◽  
Author(s):  
Amaresh Chandra Mishra ◽  
R. Giri
Keyword(s):  
Hysteresis Loop ◽  
Simulation Study ◽  
Magnetization Reversal ◽  
Hysteresis Loops ◽  
Vortex State ◽  
Micromagnetic Simulation ◽  
Hysteresis Curve ◽  
Minor Radius ◽  
Maximum Value ◽  
Major Radius

Using micromagnetic simulation, the magnetization reversal of soft permalloy rings of torus shape with major radius R varying within 20–100 nm has been investigated. The minor radius r of the torus rings was increased from 5 nm up to a maximum value r[Formula: see text] such that R- r[Formula: see text] = 10 nm. Micromagnetic simulation of in-plane hysteresis curve of these nanorings revealed that in the case of very thin rings (r [Formula: see text] 10 nm), the remanent state is found to be an onion state, whereas for all other rings, the remanent state is a vortex state. The area of the hysteresis loop was found to be decreasing gradually with the increment of r. The normalized area under the hysteresis loops (A[Formula: see text]) increases initially with increment of r. It attains a maximum for a certain value of r = r0 and again decreases thereafter. This value r0 increases as we decrease R and as a result, this peak feature is hardly visible in the case of smaller rings (rings having small R).

The Study of Magnetic Properties of Fe/Ag/Cr Thin Films

2018 ◽  
Vol 18 ◽  
pp. 1-6
Author(s):  
Radhia Boukhalfa
Keyword(s):  
Surface Roughness ◽  
Magnetic Properties ◽  
Buffer Layer ◽  
Layer Thickness ◽  
Magnetization Reversal ◽  
Kerr Effect ◽  
Uniaxial Anisotropy ◽  
Hysteresis Loops ◽  
Crystalline Substrate ◽  
Buffer Layer Thickness

(300Å)Fe films were deposited, on MgO (001) single crystalline substrate with various buffer layer thickness tAg (Å) / (75Å) Cr. The magnetic properties of the Fe films were measured by magneto-optic Kerr effect (MOKE) technique. The MOKE measurements provided the tAg buffer layer thickness dependence of the hysteresis loops and the change of loop shapes with the surface roughness. It was found that the magnetization reversal process changed with the surface roughness. Magnetization rotation dominated the magnetization reversal for the smoothest films. As the films roughened, the domain-wall pinning set in, eventually dominating the magnetization reversal for the roughest films. Additionally, the magnetic uniaxial anisotropy in the Fe films disappeared as the roughness parameters increased. It was also found from MOKE that the surface roughness strongly affected the coercivity.

scholarly journals Structure of Alloys for (Sm,Zr)(Co,Cu,Fe)z Permanent Magnets: II. Composition, Magnetization Reversal, and Magnetic Hardening of Main Structural Components

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5426
Author(s):  
Andrey G. Dormidontov ◽  
Natalia B. Kolchugina ◽  
Nikolay A. Dormidontov ◽  
Yury V. Milov ◽  
Alexander S. Andreenko
Keyword(s):  
Phase Transformations ◽  
Domain Structure ◽  
Magnetization Reversal ◽  
Permanent Magnets ◽  
Hysteresis Loops ◽  
Total Sample ◽  
High Coercivity ◽  
Metallographic Analysis ◽  
Structural Components ◽  
Slow Cooling

Experimental series of alloys for (Sm,Zr)(Co,Cu,Fe)Z permanent magnets are presented in the concentration ranges that provide wide variations of (4f)/(4d)/(3d) ratios of comprising elements. Optical metallographic analysis, observation of the surface domain structure upon magnetization reversal (Kerr effect), electron microprobe analysis, and measuring the major hysteresis loops of samples at different stages of heat treatment are used to study processes related to the development of the highly coercive state of these samples. It was found that the volume fractions of two main structural components A and B, which comprise 90% of the total sample volume, rigorously control the coercivity at all stages of thermal aging. At the same time, structural components A and B themselves in samples being in the high-coercivity state differ qualitatively and quantitatively in the chemical composition, domain structure and its development in external magnetic fields and, therefore, are characterized by different morphologies of the phases comprising the structural components. Two stages of phase transformations in the sample structure are observed. During isothermal annealing, the cellular structure develops within the B component, whereas, during stepwise (slow) cooling or quenching from the isothermal aging temperature to 400 °C, a phase structure evolves within both the cell boundaries in B and the structural component A. The degree of completion of the phase transformations within micro- and nano-volumes of the components determines the ultimate hysteretic characteristics of the material.

scholarly journals Micromagnetic Simulation of Round Ferromagnetic Nanodots with Varying Roughness and Symmetry

2021 ◽  
Vol 6 (2) ◽  
pp. 19
Author(s):  
Pia Steinmetz ◽  
Andrea Ehrmann
Keyword(s):  
Data Storage ◽  
Magnetization Reversal ◽  
Hysteresis Loops ◽  
Basic Research ◽  
Magnetic Data ◽  
Field Orientation ◽  
Thin Ring ◽  
Production Technologies ◽  
Magnetic States ◽  
The Impact

Magnetic nanodots are of high interest for basic research due to their broad spectrum of possible magnetic states and magnetization reversal processes. Besides, they are of technological interest since they can be applied in magnetic data storage, especially if vortex states occur in closed dots or open rings. While producing such nanorings and nanodots from diverse magnetic materials by lithographic techniques is quite common nowadays, these production technologies are naturally prone to small deviations of the borders of these nanoparticles. Here we investigate the influence of well-defined angular-dependent roughness of the edges, created by building the nanoparticles from small cubes, on the resulting hysteresis loops and magnetization reversal processes in five different round nanodots with varying open areas, from a thin ring to a closed nanodot. By varying the orientation of the external magnetic field, the impact of the angle-dependent roughness can be estimated. Especially for the thinnest ring, significant dependence of the transverse magnetization component on the field orientation can be found.

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