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Impact of Device Variability and Circuit Phase Shift in Synchronized Spin Torque Oscillators

Published online by Cambridge University Press:  21 March 2011

Johan Persson ,
Yan Zhou  and
Johan Akerman
Johan Persson
Affiliation:
Microelectronics and Applied Physics, Information and Communication Technology, Electrum 229, Stockholm, 16440, Sweden
Yan Zhou
Affiliation:
Microelectronics and Applied Physics, Information and Communication Technology, Electrum 229, Stockholm, 16440, Sweden
Johan Akerman
Affiliation:
Microelectronics and Applied Physics, Information and Communication Technology, Electrum 229, Stockholm, 16440, Sweden
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Abstract

Current-induced magnetization dynamics in a system composed of two electrically coupled spin torque oscillators (STOs) is examined. The dynamics of the STOs is modeled by the Landau–Lifshitz–Gilbert equations modified with a Slonczewski spin-transfer torque term. To study the impact of realistic process variations on STO synchronization we let the two STOs have different in-plane anisotropy fields (Hk). The simulation also provides for a time delay τ. We construct a phase diagram of the STO synchronization as a function of Hk and direct current (Idc) at different τ. The phase diagram turns out to be quite rich with different types of synchronized precession modes. While the synchronized state is originally very sensitive to STO process variations and can only sustain up to 4% Hk variation, the addition of a small time delay dramatically improves its robustness and allows as much as 145% Hk variation in the entire out-of-plane precession regime. It is also shown that the two STOs can not only be locked in frequency, but also in phase at a given τ and the phase difference between the two STOs can be tuned by varying the dc current.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 998: Symposium J – Nanoscale Magnetics and Device Applications , 2007 , 998-J02-06
Copyright
Copyright © Materials Research Society 2007

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