• 제목/요약/키워드: spin torque

검색결과 122건 처리시간 0.024초

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
    • /
    • 제13권1호
    • /
    • pp.28-33
    • /
    • 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.

Current-Induced Magnetic Domain-Wall Motion by Spin Transfer Torque: Collective Coordinate Approach with Domain-Wall Width Variation

  • Jung, Soon-Wook;Lee, Hyun-Woo
    • Journal of Magnetics
    • /
    • 제12권1호
    • /
    • pp.1-6
    • /
    • 2007
  • The spin transfer torque generated by a spin-polarized current can induce the shift of the magnetic domain-wall position. In this work, we study theoretically the current-induced domain-wall motion by using the collective coordinate approach [Gen Tatara and Hiroshi Kohno, Phys. Rev. Lett. 92, 86601 (2004)]. The approach is extended to include not only the domain-wall position and the polarization angle changes but also the domain-wall width variation. It is demonstrated that the width variation affects the critical current.

Advanced Circuit-Level Model of Magnetic Tunnel Junction-based Spin-Torque Oscillator with Perpendicular Anisotropy Field

  • Kim, Miryeon;Lim, Hyein;Ahn, Sora;Lee, Seungjun;Shin, Hyungsoon
    • JSTS:Journal of Semiconductor Technology and Science
    • /
    • 제13권6호
    • /
    • pp.556-561
    • /
    • 2013
  • Interest in spin-torque oscillators (STOs) has been increasing due to their potential use in communication devices. In particular the magnetic tunnel junction-based STO (MTJ-STO) with high perpendicular anisotropy is gaining attention since it can generate high output power. In this paper, a circuit-level model for an in-plane magnetized MTJ-STO with partial perpendicular anisotropy is proposed. The model includes the perpendicular torque and the shift field for more accurate modeling. The bias voltage dependence of perpendicular torque is represented as quadratic. The model is written in Verilog-A, and simulated using HSPICE simulator with a current-mirror circuit and a multi-stage wideband amplifier. The simulation results show the proposed model can accurately replicate the experimental data such that the power increases and the frequency decreases as the value of the perpendicular anisotropy gets close to the value of the demagnetizing field.

Current-induced Spin Wave Excitations in Asymmetric Nanopillar Junctions

  • Fiandimas, Arie;Lee, Kyung-Jin;Shin, Kyung-Ho
    • Journal of Magnetics
    • /
    • 제14권2호
    • /
    • pp.90-92
    • /
    • 2009
  • This study examined the current-induced spin wave excitation in asymmetric nanopillar junctions with a stack sequence of 20 nm Pt/10 nm Cu/7 nm NiFe/300 nm Cu, and a circular lateral dimension of 240 nm. An analysis of the magnetic and magnetotransport characteristics of the junction showed a possible spin transfer effect at this sample dimension when the magnetization was switched from a vortex state to another state. This finding is expected to help improve the understanding of the spin transfer torque phenomenon in nanopillar junctions.

Current-Driven Domain-Wall Depinning in Pt/CoFe/Pt Nanowires with Perpendicular Magnetic Anisotropy

  • Kim, Kab-Jin;Lee, Jae-Chul;Choe, Sug-Bong
    • Journal of Magnetics
    • /
    • 제14권3호
    • /
    • pp.101-103
    • /
    • 2009
  • The spin transfer torque efficiency was determined experimentally by observing the current-driven domainwall depinning of Pt/CoFe/Pt nanowires with perpendicular magnetic anisotropy. The depinning time was exponentially proportional to the applied magnetic field, and was well explained by the Neel-Brown formula. The depinning time and threshold magnetic field were varied considerably by injecting current into the nanowire. The spin transfer torque efficiency was estimated to be $(7.2{\pm}0.9){\times}10^{-15}Tm^2$/A from the linear dependence of the threshold current density with respect to the applied magnetic field.