| 1. |
- Sharma, R., et al.
(author)
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A high-speed single sideband generator using a magnetic tunnel junction spin torque nano-oscillator
- 2017
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7:1
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Journal article (peer-reviewed)abstract
- An important property of spin-torque nano-oscillators (STNOs) is their ability to produce a frequency modulated (FM) signal, which is very critical for communication applications. We here demonstrate a novel single sideband (SSB) modulation phenomenon using a magnetic tunnel junction (MTJ)-based STNO, which saves transmission bandwidth and in principle should minimize attenuation for wireless communication. Experimentally, lower single sidebands (LSSBs) have been successfully demonstrated over a wide range of modulation frequency, f m = 150 MHz-1 GHz. The observed LSSBs are determined by the intrinsic properties of the device, which can be modeled well by a nonlinear frequency and amplitude modulation formulation and reproduced in macrospin simulations. Moreover, our macrospin simulation results show that the range of modulation current and modulation frequency for generating SSBs can be controlled by the field-like torque and biasing conditions. © 2017 The Author(s).
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| 2. |
- Sharma, R., et al.
(author)
-
Enhanced Modulation Bandwidth of a Magnetic Tunnel Junction-Based Spin Torque Nano-Oscillator Under Strong Current Modulation
- 2021
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In: Ieee Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 42:12, s. 1886-1889
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Journal article (peer-reviewed)abstract
- The modulation bandwidth (f(BW)) is a critical figure-of-merit for wireless communication applications of spin torque nano-oscillators (STNOs) as it determines the maximum data rate. Although both theory and previous experiments have shown that f(BW) in STNOs is governed by the amplitude relaxation frequency f(p), we here demonstrate, using single-shot time-resolved measurements of a magnetic tunnel junction based STNO, that it can be many times larger under strong modulation. The behavior is qualitatively reproduced in macrospin simulations. Our results show that f(BW) of STNOs is not as limiting a factor for future wireless applications as previously believed.
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| 3. |
- Sharma, R., et al.
(author)
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Time-domain stability of parametric synchronization in a spin-torque nano-oscillator based on a magnetic tunnel junction
- 2017
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In: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 96:2
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Journal article (peer-reviewed)abstract
- We report on time-domain stability of the parametric synchronization in a spin-torque nano-oscillator (STNO) based on a magnetic tunnel junction. Time-domain measurements of the instantaneous frequency (f(i)) of a parametrically synchronized STNO showrandom short-term unlocking of the STNO signal for low injected radio-frequency (RF) power, which cannot be revealed in time-averaged frequency domain measurements. Macrospin simulations reproduce the experimental results and reveal that the random unlocking during synchronization is driven by thermal fluctuations. We show that by using a high injected RF power, random unlocking of the STNO can be avoided. However, a perfect synchronization characterized by complete suppression of phase noise, so-called phase noise squeezing, can be obtained only at a significantly higher RF power. Our macrospin simulations suggest that a lower temperature and a higher positive ratio of the fieldlike torque to the spin transfer torque reduce the threshold RF power required for phase noise squeezing under parametric synchronization.
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| 4. |
- Sisodia, Sanjay, et al.
(author)
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The effects of voids in quasi-static indentation of resin-infused reinforced polymers
- 2019
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In: Journal of composite materials. - : SAGE Publications. - 0021-9983 .- 1530-793X. ; 53:28-30, s. 4399-4410
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Journal article (peer-reviewed)abstract
- The focus of this study is the influence of voids on the damage behaviour in quasi-static loading of resin-infused carbon fibre-reinforced polymers. Experimental results are presented for quasi-static loading in combination with high-resolution tomographic imaging and statistical analysis (homology of pores or voids and induced cracks). Three distinct mechanisms were observed to control delamination growth in the presence of sharp and blunt voids. Delamination cracks interact with the supporting yarns, especially in combination with air pockets trapped in the resin in the form of long, sharp voids. This resulted in crack growth that coalesces with delamination cracks from neighbouring yarn-voids during increased out-of-plane load-displacement, with almost no presence of intralaminar transverse cracks. This highlights the benefits and drawbacks of the supporting yarn during out-of-plane loading.
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