• Title/Summary/Keyword: spin transfer torque

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Spin Torque Nano-Oscillator with an Exchange-Biased Free Rotating Layer

  • You, Chun-Yeol
    • Journal of Magnetics
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    • v.14 no.4
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    • pp.168-171
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    • 2009
  • We propose a new type of spin torque nano-oscillator structure with an exchange- biased free rotating layer. The proposed spin torque nano-oscillator consists of a fixed layer and a free rotating layer with an additional anti-ferromagnetic layer, which leads to an exchange bias in the free rotating layer. The spin dynamics of the exchange-biased free rotating layer can be described as an additional exchange field because the exchange bias manifests itself by the existance of a finite exchange bias field. The exchange bias field plays a similar role to that of a finite external field. Hence, microwave generation can be achieved without an external field in the proposed structure.

Macro-Model of Magnetic Tunnel Junction for STT-MRAM including Dynamic Behavior

  • Kim, Kyungmin;Yoo, Changsik
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.14 no.6
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    • pp.728-732
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    • 2014
  • Macro-model of magnetic tunnel junction (MTJ) for spin transfer torque magnetic random access memory (STT-MRAM) has been developed. The macro-model can describe the dynamic behavior such as the state change of MTJ as a function of the pulse width of driving current and voltage. The statistical behavior has been included in the model to represent the variation of the MTJ characteristic due to process variation. The macro-model has been developed in Verilog-A.

Spin-Torque Oscillator using a Perpendicular Polarizer with Double Free Layers

  • Seo, Soo-Man;Lee, Kyung-Jin
    • Journal of Magnetics
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    • v.13 no.4
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    • pp.153-156
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    • 2008
  • We conducted a micromagnetic modeling study to investigate the spin torque oscillator (STO) using a perpendicular polarizer. We used an additional layer of negative anisotropy constant materials (NAM) on a conventional STO. For the NAM layer, the magnetic easy plane is parallel to the in-plane easy axis of the free layer, and inhibits the development of the out-of-plane component of the magnetization in the free layer. As a result, this new type of STO provides a high frequency limit up to 50 GHz.

Analytic Model of Spin-Torque Oscillators (STO) for Circuit-Level Simulation

  • Ahn, Sora;Lim, Hyein;Shin, Hyungsoon;Lee, Seungjun
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.13 no.1
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    • pp.28-33
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    • 2013
  • Spin-torque oscillators (STO) is a new device that can be used as a tunable microwave source in various wireless devices. Spin-transfer torque effect in magnetic multilayered nanostructure can induce precession of magnetization when bias current and external magnetic field are properly applied, and a microwave signal is generated from that precession. We proposed a semi-empirical circuit-level model of an STO in previous work. In this paper, we present a refined STO model which gives more accuracy by considering physical phenomena in the calculation of effective field. Characteristics of the STO are expressed as functions of external magnetic field and bias current in Verilog-A HDL such that they can be simulated with circuit-level simulators such as Hspice. The simulation results are in good agreement with the experimental data.

Technology Trend of Spin-Transfer-Torque Magnetoresistive Random Access Memory (STT-MRAM) (스핀전달토크형 자기저항메모리(STT-MRAM) 기술개발 동향)

  • Kim, D.K.;Cho, J.U.;Noh, S.J.;Kim, Y.K.
    • Journal of the Korean Magnetics Society
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    • v.19 no.1
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    • pp.22-27
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    • 2009
  • Reduction of the critical current density ($J_c$) for STT magnetization switching is most important issue of magnetic tunnel junctions (MTJs) based MRAM. This report describes how to decrease the Jc and will introduce the recent research progresses of STT-MRAM devices with material engineering and structural improvement, respectively.