Tuning Resonance Frequency of Spin Wave Localized in an Isolated Skyrmion by Magnetoelectric Couplings

Understanding the dynamic behavior of an isolated skyrmion with external perturbations has been obstructed due to the difficulty in experimentally observing such an instantaneous phenomenon within picoseconds. Herein, we theoretically investigated the spin-transfer-torque-induced dynamics of an isolated skyrmion excited by external nanosecond-pulse perturbations. It is found that a redshift of the resonant frequency appears under a pulse polarized current with [Formula: see text][Formula: see text]A/m2 and [Formula: see text][Formula: see text]GHz, while a blueshift is presented under a combined perturbation of the pulse polarized current and an out-of-plane ac magnetic field. The physic origins of the redshift and the blueshift are ascribed to the increased average energy of system from [Formula: see text][Formula: see text]J to [Formula: see text][Formula: see text]J and integer multiple (twofold and fourfold) oscillation frequencies of total energy, respectively. The present study could thus provide an insight to the micromagnetic dynamics of skyrmion under the magnetoelectric couplings.

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CORIDOR: Using CO herence and Tempo R al Local I ty to Mitigate Read D isurbance Err OR in STT-RAM Caches

ACM Transactions on Embedded Computing Systems ◽

10.1145/3484493 ◽

2022 ◽

Vol 21 (1) ◽

pp. 1-24

Author(s):

Sheel Sindhu Manohar ◽

Sparsh Mittal ◽

Hemangee K. Kapoor

Keyword(s):

Total Energy ◽

Energy Saving ◽

Energy Savings ◽

Spin Transfer Torque ◽

Spin Transfer ◽

Read Operation ◽

Near Future ◽

The Ideal

In the deep sub-micron region, “spin-transfer torque RAM” (STT-RAM ) suffers from “read-disturbance error” (RDE) , whereby a read operation disturbs the stored data. Mitigation of RDE requires restore operations, which imposes latency and energy penalties. Hence, RDE presents a crucial threat to the scaling of STT-RAM. In this paper, we offer three techniques to reduce the restore overhead. First, we avoid the restore operations for those reads, where the block will get updated at a higher level cache in the near future. Second, we identify read-intensive blocks using a lightweight mechanism and then migrate these blocks to a small SRAM buffer. On a future read to these blocks, the restore operation is avoided. Third, for data blocks having zero value, a write operation is avoided, and only a flag is set. Based on this flag, both read and restore operations to this block are avoided. We combine these three techniques to design our final policy, named CORIDOR. Compared to a baseline policy, which performs restore operation after each read, CORIDOR achieves a 31.6% reduction in total energy and brings the relative CPI (cycle-per-instruction) to 0.64×. By contrast, an ideal RDE-free STT-RAM saves 42.7% energy and brings the relative CPI to 0.62×. Thus, our CORIDOR policy achieves nearly the same performance as an ideal RDE-free STT-RAM cache. Also, it reaches three-fourths of the energy-saving achieved by the ideal RDE-free cache. We also compare CORIDOR with four previous techniques and show that CORIDOR provides higher restore energy savings than these techniques.

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Field Dependence of Switching Currents in an Exchange Biased Spin Valve

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2007.18033 ◽

2007 ◽

Vol 7 (1) ◽

pp. 344-349

Author(s):

Hoang Yen Thi Nguyen ◽

Sung-Jung Joo ◽

Kuyoul Jung ◽

Kyung-Ho Shin

Keyword(s):

Magnetic Field ◽

Field Dependence ◽

Spin Valve ◽

Spin Transfer Torque ◽

Information Storage ◽

Spin Transfer ◽

Field Range ◽

Higher Spin ◽

Thermal Magnetization ◽

Negative Field

Current induced magnetic reversal due to spin transfer torque is a promising candidate in advanced information storage technology. It has been intensively studied. This work reports the field-dependence of switching-currents for current induced magnetization switching in a uncoupled nano-sized cobalt-based spin valve of exchange biased type. The dependency is investigated in hysteretic regime at room temperature, in comparison with that of a trilayer simple spin valve. In the simple spin valve, the switching currents behave to the positive and the negative applied magnetic field symmetrically. In the exchange biased type, in contrast, the switching currents respond to the negative field in a quite unusual and different manner than to the positive field. A negative magnetic field then can shift the switching-currents into either negative or positive current range, dependently on whether a parallel or an antiparallel state of the spin valve was produced by that field. This different character of switching currents in the negative field range can be explained by the effect of the exchange bias pinning field on the spin-polarizer (the fixed Co layer) of the exchange biased spin valve. That unidirectional pinning filed could suppress the thermal magnetization fluctuation in the spin-polarizer, leading to a higher spin polarization of the current, and hence a lower switching current density than in the simple spin valve.

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