scholarly journals Magnetic droplet nucleation boundary in orthogonal spin-torque nano-oscillators

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Sunjae Chung ◽  
Anders Eklund ◽  
Ezio Iacocca ◽  
Seyed Majid Mohseni ◽  
Sohrab R. Sani ◽  
...  
Keyword(s):  
Critical Role ◽  
Perpendicular Magnetic Anisotropy ◽  
Accurate Method ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Spin Torque ◽  
Droplet Nucleation ◽  
Wide Range ◽  
Field Plane

Abstract Static and dynamic magnetic solitons play a critical role in applied nanomagnetism. Magnetic droplets, a type of non-topological dissipative soliton, can be nucleated and sustained in nanocontact spin-torque oscillators with perpendicular magnetic anisotropy free layers. Here, we perform a detailed experimental determination of the full droplet nucleation boundary in the current–field plane for a wide range of nanocontact sizes and demonstrate its excellent agreement with an analytical expression originating from a stability analysis. Our results reconcile recent contradicting reports of the field dependence of the droplet nucleation. Furthermore, our analytical model both highlights the relation between the fixed layer material and the droplet nucleation current magnitude, and provides an accurate method to experimentally determine the spin transfer torque asymmetry of each device.

scholarly journals Spin Torque Oscillator for High Performance Magnetic Memory

2015 ◽  
Vol 20 (1) ◽  
pp. 77
Author(s):  
Rachid Sbiaa ◽  
Khaled Bouziane
Keyword(s):  
High Performance ◽  
Perpendicular Magnetic Anisotropy ◽  
Magnetic Tunnel Junction ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Magnetic Memory ◽  
Spin Torque ◽  
Free Layer ◽  
Switching Current ◽  
Thermal Stability Of

A study on spin transfer torque switching in a magnetic tunnel junction with perpendicular magnetic anisotropy is presented. The switching current can be strongly reduced under a spin torque oscillator (STO), and its use in addition to the conventional transport in magnetic tunnel junctions (MTJ) should be considered. The reduction of the switching current from the parallel state to the antiparallel state is greater than in  the opposite direction, thus minimizing the asymmetry of the resistance versus current in the hysteresis loop. This reduction of both switching current and asymmetry under a spin torque oscillator occurs only during the writing process and does not affect the thermal stability of the free layer.

scholarly journals Current-induced spin–orbit torques

2011 ◽  
Vol 369 (1948) ◽  
pp. 3175-3197 ◽  
Author(s):  
Pietro Gambardella ◽  
Ioan Mihai Miron
Keyword(s):  
Angular Momentum ◽  
Exchange Coupling ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Spin Torque ◽  
Inversion Symmetry ◽  
Spin Orbit ◽  
Great Flexibility ◽  
Combined Action ◽  
Proper Material

The ability to reverse the magnetization of nanomagnets by current injection has attracted increased attention ever since the spin-transfer torque mechanism was predicted in 1996. In this paper, we review the basic theoretical and experimental arguments supporting a novel current-induced spin torque mechanism taking place in ferromagnetic (FM) materials. This effect, hereafter named spin–orbit (SO) torque, is produced by the flow of an electric current in a crystalline structure lacking inversion symmetry, which transfers orbital angular momentum from the lattice to the spin system owing to the combined action of SO and exchange coupling. SO torques are found to be prominent in both FM metal and semiconducting systems, allowing for great flexibility in adjusting their orientation and magnitude by proper material engineering. Further directions of research in this field are briefly outlined.

Magnetization switching by magnon-mediated spin torque through an antiferromagnetic insulator

Science ◽  
2019 ◽  
Vol 366 (6469) ◽  
pp. 1125-1128 ◽  
Author(s):  
Yi Wang ◽  
Dapeng Zhu ◽  
Yumeng Yang ◽  
Kyusup Lee ◽  
Rahul Mishra ◽  
...  
Keyword(s):  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Spin Torque ◽  
Local Magnetization ◽  
Magnetization Switching ◽  
Spintronic Devices ◽  
Magnetic Devices ◽  
Alternative Approach ◽  
Efficient Control ◽  
Electrical Spin

Widespread applications of magnetic devices require an efficient means to manipulate the local magnetization. One mechanism is the electrical spin-transfer torque associated with electron-mediated spin currents; however, this suffers from substantial energy dissipation caused by Joule heating. We experimentally demonstrated an alternative approach based on magnon currents and achieved magnon-torque–induced magnetization switching in Bi2Se3/antiferromagnetic insulator NiO/ferromagnet devices at room temperature. The magnon currents carry spin angular momentum efficiently without involving moving electrons through a 25-nanometer-thick NiO layer. The magnon torque is sufficient to control the magnetization, which is comparable with previously observed electrical spin torque ratios. This research, which is relevant to the energy-efficient control of spintronic devices, will invigorate magnon-based memory and logic devices.

scholarly journals Multiple purpose spin transfer torque operated devices

2013 ◽  
Vol 26 (3) ◽  
pp. 227-238
Author(s):  
Thomas Windbacher ◽  
Hiwa Mahmoudi ◽  
Alexander Makarov ◽  
Viktor Sverdlov ◽  
Siegfried Selberherr
Keyword(s):  
Information Processing ◽  
Building Block ◽  
Energy Efficient ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Spin Torque ◽  
Logic Device ◽  
Flip Flop ◽  
Sequential Logic ◽  
Efficient Information

We summarize our recent work on a non-volatile logic building block required for energy-efficient information processing systems. A sequential logic device, in particular, an alternative non-volatile magnetic flip-flop has been introduced. Its properties are investigated and its extension to a very dense shift register is demonstrated. We show that the flip-flop structure inherently exhibits oscillations and discuss its spin torque nano-oscillator properties.

Enhancing Frequency and Reducing the Power of Spin-Torque Nanooscillator By The Generated Oersted Field

SPIN ◽  
2020 ◽  
Vol 10 (02) ◽  
pp. 2050012
Author(s):  
H. Bhoomeeswaran ◽  
P. Sabareesan
Keyword(s):  
Spin Valve ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Spin Torque ◽  
Spintronic Devices ◽  
Frequency Tunability ◽  
Spin Polarized ◽  
The Individual ◽  
Promising Source ◽  
Nonmagnetic Spacer

The current-driven magnetization precession dynamics stimulated by Spin-Transfer Torque (STT) in a trilayer spin-valve device (typically Spin-Torque Nanooscillator (STNO)) is numerically investigated by solving the Landau–Lifshitz–Gilbert–Slonczewski (LLGS) equation. We have devised four STNO devices made of ferromagnetic alloys such as CoPt, CoFeB, Fe[Formula: see text]B[Formula: see text]Ni2 and EuO, which act as free and fixed layers. Here, copper acts as a nonmagnetic spacer for all the devices. In this work, we have introduced the current-induced Oersted field, which is generated when a spin-polarized current passes through the device. The generated Oersted field strength is varied by increasing the diameter of the STNO device. Frequency tunability is achieved in all the four devices, whereas the power of the individual device reduces. The frequency and power of the devices depend entirely on the saturation magnetization of the material, which inherently reflects in the current density and the coherence of the spin-polarized DC. In all devices, the frequency increases, whereas the power decreases by increasing the strength of the Oersted field. Among the four devices, the maximum frequency can be tuned up to 104[Formula: see text]GHz with 40[Formula: see text]nm device diameter, which is obtained for EuO material. This opens a promising source and paves a glittering future for the nanoscale spintronic devices.

scholarly journals A New Circuit Model for Spin-Torque Oscillator Including Perpendicular Torque of Magnetic Tunnel Junction

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Hyein Lim ◽  
Sora Ahn ◽  
Miryeon Kim ◽  
Seungjun Lee ◽  
Hyungsoon Shin
Keyword(s):  
Tunnel Junction ◽  
Giant Magnetoresistance ◽  
New Technology ◽  
Magnetic Tunnel Junction ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Spin Torque ◽  
Mean Oscillation ◽  
Proposed Model ◽  
Level Model

Spin-torque oscillator (STO) is a promising new technology for the future RF oscillators, which is based on the spin-transfer torque (STT) effect in magnetic multilayered nanostructure. It is expected to provide a larger tunability, smaller size, lower power consumption, and higher level of integration than the semiconductor-based oscillators. In our previous work, a circuit-level model of the giant magnetoresistance (GMR) STO was proposed. In this paper, we present a physics-based circuit-level model of the magnetic tunnel junction (MTJ)-based STO. MTJ-STO model includes the effect of perpendicular torque that has been ignored in the GMR-STO model. The variations of three major characteristics, generation frequency, mean oscillation power, and generation linewidth of an MTJ-STO with respect to the amount of perpendicular torque, are investigated, and the results are applied to our model. The operation of the model was verified by HSPICE simulation, and the results show an excellent agreement with the experimental data. The results also prove that a full circuit-level simulation with MJT-STO devices can be made with our proposed model.

TETRAGONAL HEUSLER-LIKE Mn–Ga ALLOYS BASED PERPENDICULAR MAGNETIC TUNNEL JUNCTIONS

SPIN ◽  
2014 ◽  
Vol 04 (04) ◽  
pp. 1440024 ◽  
Author(s):  
QINLI MA ◽  
ATSUSHI SUGIHARA ◽  
KAZUYA SUZUKI ◽  
XIANMIN ZHANG ◽  
TERUNOBU MIYAZAKI ◽  
...  
Keyword(s):  
Tunnel Junctions ◽  
Random Access ◽  
Magnetic Tunnel Junctions ◽  
Perpendicular Magnetic Anisotropy ◽  
Random Access Memory ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Current Status ◽  
Access Memory ◽  
Magnetic Random Access Memory

Films of the Mn -based tetragonal Heusler-like alloys, such as Mn – Ga , exhibit a large perpendicular magnetic anisotropy (PMA), small damping constant, small saturation magnetization and large spin polarizations. These properties are attractive for the application to the next generation high density spin-transfer-torque (STT) magnetic random access memory (STT-MRAM). We reviewed the structure, magnetic properties and Gilbert damping of the alloy films with large PMA, and the current status of research on tunnel magnetoresistance (TMR) in perpendicular magnetic tunnel junctions (p-MTJs) based on Mn -based tetragonal Heusler-like alloy electrode, and also discuss the issues for the application of those to STT-MRAM.

scholarly journals A Survey on the Modeling of Magnetic Tunnel Junctions for Circuit Simulation

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Hyein Lim ◽  
Seungjun Lee ◽  
Hyungsoon Shin
Keyword(s):  
Low Power ◽  
Tunnel Junctions ◽  
Magnetic Tunnel Junctions ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Switching Behavior ◽  
Behavioral Models ◽  
Physical Mechanisms ◽  
Wide Range ◽  
Voltage Dependent

Spin-transfer torque-based magnetoresistive random access memory (STT-MRAM) is a promising candidate for universal memory that may replace traditional memory forms. It is expected to provide high-speed operation, scalability, low-power dissipation, and high endurance. MRAM switching technology has evolved from the field-induced magnetic switching (FIMS) technique to the spin-transfer torque (STT) switching technique. Additionally, material technology that induces perpendicular magnetic anisotropy (PMA) facilitates low-power operation through the reduction of the switching current density. In this paper, the modeling of magnetic tunnel junctions (MTJs) is reviewed. Modeling methods and models of MTJ characteristics are classified into two groups, macromodels and behavioral models, and the most important characteristics of MTJs, the voltage-dependent MTJ resistance and the switching behavior, are compared. To represent the voltage dependency of MTJ resistance, some models are based on physical mechanisms, such as Landau-Lifshitz-Gilbert (LLG) equation or voltage-dependent conductance. Some behavioral models are constructed by adding fitting parameters or introducing new physical parameters to represent the complex switching behavior of an MTJ over a wide range of input current conditions. Other models that are not based on physical mechanisms are implemented by simply fitting to experimental data.

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