Robust skyrmion mediated reversal of ferromagnetic nanodots of 20 nm lateral dimension with high Ms and observable DMI

AbstractImplementation of skyrmion based energy efficient and high-density data storage devices requires aggressive scaling of skyrmion size. Ferrimagnetic materials are considered to be a suitable platform for this purpose due to their low saturation magnetization (i.e. smaller stray field). However, this method of lowering the saturation magnetization and scaling the lateral size of skyrmions is only applicable where the skyrmions have a smaller lateral dimension compared to the hosting film. Here, we show by performing rigorous micromagnetic simulation that the size of skyrmions, which have lateral dimension comparable to their hosting nanodot can be scaled by increasing saturation magnetization. Also, when the lateral dimension of nanodot is reduced and thereby the skyrmion confined in it is downscaled, there remains a challenge in forming a stable skyrmion with experimentally observed Dzyaloshinskii–Moriya interaction (DMI) values since this interaction has to facilitate higher canting per spin to complete a 360° rotation along the diameter. In our study, we found that skyrmions can be formed in 20 nm lateral dimension nanodots with high saturation magnetization (1.30–1.70 MA/m) and DMI values (~ 3 mJ/m2) that have been reported to date. This result could stimulate experiments on implementation of highly dense skyrmion devices. Additionally, using this, we show that voltage controlled magnetic anisotropy based switching mediated by an intermediate skyrmion state can be achieved in the soft layer of a ferromagnetic p-MTJ of lateral dimensions 20 nm with sub 1 fJ/bit energy in the presence of room temperature thermal noise with reasonable DMI ~ 3 mJ/m2.

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Preparation and performance of CuFe2O4 and ZnFe2O4 magnetic nanocrystals

Materials Research Express ◽

10.1088/2053-1591/ac40b6 ◽

2021 ◽

Author(s):

Q.G Jia ◽

S.H. Liang ◽

Q.X Wang

Keyword(s):

Saturation Magnetization ◽

Crystal Structures ◽

Room Temperature ◽

Magnetic Nanocrystals ◽

And Performance ◽

Spinel Structures ◽

20 Nm

Abstract Based on the coprecipitation of FeSO4(NH4)2SO4 with CuCl2 and ZnSO4, CuFe2O4 and ZnFe2O4 nanocrystals were successfully synthesized. The morphology and the crystal structures of the nanoparticles were studied via SEM, TEM and XRD, which showed that MFe2O4 samples were formed aggregated nanoparticles with crystal sizes of 16~20 nm with a narrow dispersion in size. The samples had the typical spinel structures. Magnetic analyses demonstrated that the CuFe2O4 sample had the saturation magnetization (Ms) of 10.10 emu/g with the coercivity of 3459.39 Oe, while the ZnFe2O4 sample had the Ms of 8.27 emu/g with the coercivity of 25.42 Oe at room temperature, respectively.

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Energy-Efficient Hybrid Spintronic–Straintronic Nonvolatile Reconfigurable Equality Bit Comparator

SPIN ◽

10.1142/s2010324717500047 ◽

2017 ◽

Vol 07 (02) ◽

pp. 1750004 ◽

Cited By ~ 2

Author(s):

Ayan K. Biswas ◽

Jayasimha Atulasimha ◽

Supriyo Bandyopadhyay

Keyword(s):

Energy Efficient ◽

Room Temperature ◽

Thermal Noise ◽

Spin Valve ◽

Remote Memory ◽

Tunneling Junction ◽

Input Stream ◽

Two Phase ◽

Magnetization State ◽

Reference Stream

We propose and analyze a “spintronic/straintronic” reconfigurable equality bit comparator implemented with a nanowire spin valve whose two contacts are two-phase multiferroic nanomagnets and possess bistable magnetization. A reference bit is “written” into a stable magnetization state of one contact and an input bit in that of the other with electrically generated strain. The spin-valve’s resistance is lowered (raised) if the bits match (do not match). Multiple comparators can be interfaced in parallel with a magneto-tunneling junction to determine if an [Formula: see text]-bit input stream matches an [Formula: see text]-bit reference stream bit by bit. The system is robust against thermal noise at room temperature and a 16-bit comparator can operate at [Formula: see text][Formula: see text]MHz while dissipating [Formula: see text][Formula: see text]28[Formula: see text]fJ per cycle. This implementation is more energy-efficient than CMOS-based implementations and the reference bits can be stored in the comparator itself without the need for refresh cycles or the need to fetch them from a remote memory for comparison. That improves reliability, speed and security.

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Formation and current-induced motion of synthetic antiferromagnetic skyrmion bubbles

Nature Communications ◽

10.1038/s41467-019-13182-6 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 24

Author(s):

Takaaki Dohi ◽

Samik DuttaGupta ◽

Shunsuke Fukami ◽

Hideo Ohno

Keyword(s):

Hall Effect ◽

Current Density ◽

Energy Efficient ◽

Topological Charge ◽

Room Temperature ◽

Threshold Current ◽

Threshold Current Density ◽

New Directions ◽

Induced Motion ◽

Moriya Interaction

AbstractSkyrmion, a topologically-protected soliton, is known to emerge via electron spin in various magnetic materials. The magnetic skyrmion can be driven by low current density and has a potential to be stabilized in nanoscale, offering new directions of spintronics. However, there remain some fundamental issues in widely-studied ferromagnetic systems, which include a difficulty to realize stable ultrasmall skyrmions at room temperature, presence of the skyrmion Hall effect, and limitation of velocity owing to the topological charge. Here we show skyrmion bubbles in a synthetic antiferromagnetic coupled multilayer that are free from the above issues. Additive Dzyaloshinskii-Moriya interaction and spin-orbit torque (SOT) of the tailored stack allow stable skyrmion bubbles at room temperature, significantly smaller threshold current density or higher speed for motion, and negligible skyrmion Hall effect, with a potential to be scaled down to nanometer dimensions. The results offer a promising pathway toward nanoscale and energy-efficient skyrmion-based devices.

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Flexible Multistate Data Storage Devices Fabricated Using Natural Lignin at Room Temperature

ACS Applied Materials & Interfaces ◽

10.1021/acsami.6b14566 ◽

2017 ◽

Vol 9 (7) ◽

pp. 6207-6212 ◽

Cited By ~ 34

Author(s):

Youngjun Park ◽

Jang-Sik Lee

Keyword(s):

Data Storage ◽

Room Temperature ◽

Storage Devices ◽

Natural Lignin

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Large anomalous Hall effect driven by a nonvanishing Berry curvature in the noncolinear antiferromagnet Mn3Ge

Science Advances ◽

10.1126/sciadv.1501870 ◽

2016 ◽

Vol 2 (4) ◽

pp. e1501870 ◽

Cited By ~ 240

Author(s):

Ajaya K. Nayak ◽

Julia Erika Fischer ◽

Yan Sun ◽

Binghai Yan ◽

Julie Karel ◽

...

Keyword(s):

Hall Effect ◽

Data Storage ◽

Room Temperature ◽

Theoretical Calculations ◽

Anomalous Hall Effect ◽

Spin Hall Effect ◽

Storage Devices ◽

Berry Curvature ◽

Ferromagnetic Metals ◽

Hall Effect Measurements

It is well established that the anomalous Hall effect displayed by a ferromagnet scales with its magnetization. Therefore, an antiferromagnet that has no net magnetization should exhibit no anomalous Hall effect. We show that the noncolinear triangular antiferromagnet Mn3Ge exhibits a large anomalous Hall effect comparable to that of ferromagnetic metals; the magnitude of the anomalous conductivity is ~500 (ohm·cm)−1 at 2 K and ~50 (ohm·cm)−1 at room temperature. The angular dependence of the anomalous Hall effect measurements confirms that the small residual in-plane magnetic moment has no role in the observed effect except to control the chirality of the spin triangular structure. Our theoretical calculations demonstrate that the large anomalous Hall effect in Mn3Ge originates from a nonvanishing Berry curvature that arises from the chiral spin structure, and that also results in a large spin Hall effect of 1100 (ħ/e) (ohm·cm)−1, comparable to that of platinum. The present results pave the way toward the realization of room temperature antiferromagnetic spintronics and spin Hall effect–based data storage devices.

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The Structure and Magnetic Properties of NiZn-Ferrite Films Deposited by Magnetron Sputtering at Room Temperature

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.690-693.1702 ◽

2013 ◽

Vol 690-693 ◽

pp. 1702-1706 ◽

Cited By ~ 2

Author(s):

Shuang Jun Nie ◽

Hao Geng ◽

Jun Bao Wang ◽

Lai Sen Wang ◽

Zhen Wei Wang ◽

...

Keyword(s):

Thin Films ◽

Magnetic Properties ◽

Magnetron Sputtering ◽

Saturation Magnetization ◽

Room Temperature ◽

Oxygen Flow ◽

Flow Ratio ◽

Study Results ◽

Ferrite Thin Films ◽

Ferrite Films

NiZn-ferrite thin films were deposited onto silicon and glass substrates by radio frequency magnetron sputtering at room temperature. The effects of the relative oxygen flow ratio on the structure and magnetic properties of the thin films were investigated. The study results reveal that the films deposited under higher relative oxygen flow ratio show a better crystallinity. Static magnetic measurement results indicated that the saturation magnetization of the films was greatly affected by the crystallinity, grain dimension, and cation distribution in the NiZn-ferrite films. The NiZn-ferrite thin films with a maximum saturation magnetization of 151 emucm-3, which is about 40% of the bulk NiZn ferrite, was obtained under relative oxygen flow ratio of 60%.

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Reducing Dzyaloshinskii-Moriya interaction and field-free spin-orbit torque switching in synthetic antiferromagnets

Nature Communications ◽

10.1038/s41467-021-23414-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Ruyi Chen ◽

Qirui Cui ◽

Liyang Liao ◽

Yingmei Zhu ◽

Ruiqi Zhang ◽

...

Keyword(s):

Domain Wall ◽

Tunnel Junctions ◽

Low Power Consumption ◽

Stray Field ◽

Magnetic Memory ◽

Spin Orbit ◽

Theoretic Analysis ◽

Spintronic Devices ◽

Deterministic Switching ◽

Moriya Interaction

AbstractPerpendicularly magnetized synthetic antiferromagnets (SAF), possessing low net magnetization and high thermal stability as well as easy reading and writing characteristics, have been intensively explored to replace the ferromagnetic free layers of magnetic tunnel junctions as the kernel of spintronic devices. So far, utilizing spin-orbit torque (SOT) to realize deterministic switching of perpendicular SAF have been reported while a large external magnetic field is typically needed to break the symmetry, making it impractical for applications. Here, combining theoretic analysis and experimental results, we report that the effective modulation of Dzyaloshinskii-Moriya interaction by the interfacial crystallinity between ferromagnets and adjacent heavy metals plays an important role in domain wall configurations. By adjusting the domain wall configuration between Bloch type and Néel type, we successfully demonstrate the field-free SOT-induced magnetization switching in [Co/Pd]/Ru/[Co/Pd] SAF devices constructed with a simple wedged structure. Our work provides a practical route for utilization of perpendicularly SAF in SOT devices and paves the way for magnetic memory devices with high density, low stray field, and low power consumption.

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Wearable energy efficient fitness tracker for sports person health monitoring application

Journal of Intelligent & Fuzzy Systems ◽

10.3233/jifs-219008 ◽

2021 ◽

pp. 1-10

Author(s):

Yongyue Huang ◽

Min Hu ◽

BalaAnand Muthu ◽

R. Gayathri

Keyword(s):

Energy Consumption ◽

Data Storage ◽

Energy Efficient ◽

Consumer Satisfaction ◽

Form Factors ◽

Recognition System ◽

Energy Utilization ◽

Biologically Inspired Algorithms ◽

Enhance Efficiency ◽

Fitness Tracker

Continuous evaluation of biological and physiological metrics of sports personalities, evaluating general health status, and alerting for life-saving treatments, is supposed to enhance efficiency and healthy performance. Wearable devices with acceptable form factors compact, flexibility, minimal power consumption, etc., are needed for continuous monitoring to avoid affecting everyday operations, thereby retaining functional effectiveness and consumer satisfaction. This research focuses on the acceleration tracker for particularizing the work. Acceleration data is typically collected on battery-powered sensors for activity detection, referring to an exchange between high-precision detection and energy-efficient processing. From a feature selection perspective, the paper explores this trade-off. It suggests an Energy-Efficient Behavior Recognition System with a comprehensive energy utilization model and the Multi-objective Algorithm of Particle Swarm Optimization (EEBRS-MPSO). Therefore, using Random Forest (RF) classifiers, the model and algorithm are tested to measure the precision of identification and obtain the task’s best performance with the lowest energy consumption, among other biologically-inspired algorithms. The findings indicate that energy consumption for data storage and data processing is minimized with magnitude relative to the raw data method by choosing suitable groups of attributes. Thus, the platform allows a scalable range of feature clusters that require the authors to provide an adequate power adjustment for given target use.

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