scholarly journals Multiferroicity and skyrmions carrying electric polarization in GaV4S8

2015 ◽  
Vol 1 (10) ◽  
pp. e1500916 ◽  
Author(s):  
Eugen Ruff ◽  
Sebastian Widmann ◽  
Peter Lunkenheimer ◽  
Vladimir Tsurkan ◽  
Sandor Bordács ◽  
...  
Keyword(s):  
Data Storage ◽  
Electric Fields ◽  
Magnetic Phase Diagram ◽  
Basic Research ◽  
Electric Polarization ◽  
Spatial Modulation ◽  
Magnetic Data ◽  
Orbital Ordering ◽  
Microscopic Mechanism ◽  
Polar Crystal

Skyrmions are whirl-like topological spin objects with high potential for future magnetic data storage. A fundamental question that is relevant to both basic research and application is whether ferroelectric (FE) polarization can be associated with skyrmions’ magnetic texture and whether these objects can be manipulated by electric fields. We study the interplay between magnetism and electric polarization in the lacunar spinel GaV4S8, which undergoes a structural transition associated with orbital ordering at 44 K and reveals a complex magnetic phase diagram below 13 K, including ferromagnetic, cycloidal, and Néel-type skyrmion lattice (SkL) phases. We found that the orbitally ordered phase of GaV4S8 is FE with a sizable polarization of ~1 μC/cm2. Moreover, we observed spin-driven excess polarizations in all magnetic phases; hence, GaV4S8 hosts three different multiferroic phases with coexisting polar and magnetic order. These include the SkL phase, where we predict a strong spatial modulation of FE polarization close to the skyrmion cores. By taking into account the crystal symmetry and spin patterns of the magnetically ordered phases, we identify exchange striction as the main microscopic mechanism behind the spin-driven FE polarization in each multiferroic phase. Because GaV4S8 is unique among known SkL host materials owing to its polar crystal structure and the observed strong magnetoelectric effect, this study is an important step toward the nondissipative electric field control of skyrmions.

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.

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 Nanostructured ZnFe2O4: An Exotic Energy Material

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1286
Author(s):  
Murtaza Bohra ◽  
Vidya Alman ◽  
Rémi Arras
Keyword(s):  
Data Storage ◽  
Smart Materials ◽  
Energy Demand ◽  
Ceramic Materials ◽  
Magnetic Data ◽  
Processing Route ◽  
Energy Storage Devices ◽  
Storage Devices ◽  
Reduced Toxicity ◽  
Cation Arrangement

More people, more cities; the energy demand increases in consequence and much of that will rely on next-generation smart materials. Zn-ferrites (ZnFe2O4) are nonconventional ceramic materials on account of their unique properties, such as chemical and thermal stability and the reduced toxicity of Zn over other metals. Furthermore, the remarkable cation inversion behavior in nanostructured ZnFe2O4 extensively cast-off in the high-density magnetic data storage, 5G mobile communication, energy storage devices like Li-ion batteries, supercapacitors, and water splitting for hydrogen production, among others. Here, we review how aforesaid properties can be easily tuned in various ZnFe2O4 nanostructures depending on the choice, amount, and oxidation state of metal ions, the specific features of cation arrangement in the crystal lattice and the processing route used for the fabrication.

Thermodynamic aspects of epitaxial self-assembly and magnetoelectric response in multiferroic nanostructures

2007 ◽  
Vol 22 (8) ◽  
pp. 2087-2095 ◽  
Author(s):  
Julia Slutsker ◽  
Zhuopeng Tan ◽  
Alexander L. Roytburd ◽  
Igor Levin
Keyword(s):  
Electric Fields ◽  
Self Assembly ◽  
Electromagnetic Coupling ◽  
Hysteretic Behavior ◽  
Microscopic Mechanism ◽  
Magnetic Nanorods ◽  
External Electric Fields ◽  
Multiferroic Films ◽  
Magnetoelectric Response ◽  
Theoretical Results

A thermodynamic approach was used to describe the formation and magnetoelectric response of composite multiferroic films. Experimental and theoretical results that address the origins of different phase morphologies in epitaxial spinel-perovskite nanostructures grown on differently oriented substrates are presented. A theoretical model of magnetoelectric coupling in multiferroic nanostructures that considers a microscopic mechanism of magnetization in single-domain magnetic nanorods is described. This model explains a discontinuous electromagnetic coupling, as observed experimentally, and predicts a hysteretic behavior of magnetization under external electric fields.

scholarly journals Stacking-engineered ferroelectricity in bilayer boron nitride

Science ◽  
2021 ◽  
pp. eabd3230
Author(s):  
Kenji Yasuda ◽  
Xirui Wang ◽  
Kenji Watanabe ◽  
Takashi Taniguchi ◽  
Pablo Jarillo-Herrero
Keyword(s):  
Boron Nitride ◽  
Nonvolatile Memory ◽  
Rational Design ◽  
Parent Compound ◽  
High Mobility ◽  
Building Blocks ◽  
Electric Polarization ◽  
Experimental Realization ◽  
Polar Crystal ◽  
Memory Applications

2D ferroelectrics with robust polarization down to atomic thicknesses provide building blocks for functional heterostructures. Experimental realization remains challenging because of the requirement of a layered polar crystal. Here, we demonstrate a rational design approach to engineering 2D ferroelectrics from a non-ferroelectric parent compound via employing van der Waals assembly. Parallel-stacked bilayer boron nitride exhibits out-of-plane electric polarization that reverses depending on the stacking order. The polarization switching is probed via the resistance of an adjacently stacked graphene sheet. Twisting the boron nitride sheets by a small angle changes the dynamics of switching thanks to the formation of moiré ferroelectricity with staggered polarization. The ferroelectricity persists to room temperature while keeping the high mobility of graphene, paving the way for potential ultrathin nonvolatile memory applications.

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