We studied spin-transfer-torque (STT) switching of a cross-shaped magnetic tunnel junction in a recent report [Roy et al., J. Appl. Phys. 113, 223904 (2013)]. In that structure, the free layer is designed to have four stable energy states using the shape anisotropy of a cross. STT switching showed different regions with increasing current density. Here, we employ the micromagnetic spectral mapping technique in an attempt to understand how the asymmetry of cross dimensions and spin polarization direction of the injected current affect the magnetization dynamics. We compute spatially averaged frequency-domain spectrum of the time-domain magnetization dynamics in the presence of the current-induced STT term. At low currents, the asymmetry of polarization direction and that of the arms are observed to cause a splitting of the excited frequency modes. Higher harmonics are also observed, presumably due to spin-wave wells caused by the regions of spatially non-uniform effective magnetic field. The results could be used towards designing a multi-bit-per-cell STT-based random access memory with an improved storage density.
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7 May 2014
PROCEEDINGS OF THE 55TH ANNUAL CONFERENCE ON MAGNETISM AND MAGNETIC MATERIALS
14-18 November 2010
Atlanta, Georgia
Research Article|
Magnetism and Magnetic Materials|
January 29 2014
Micromagnetic simulations of spin-wave normal modes and the spin-transfer-torque driven magnetization dynamics of a ferromagnetic cross
Tanmoy Pramanik;
Tanmoy Pramanik
a)
1
Microelectronics Research Center, University of Texas at Austin
, Texas 78758, USA
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Urmimala Roy;
Urmimala Roy
1
Microelectronics Research Center, University of Texas at Austin
, Texas 78758, USA
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Maxim Tsoi;
Maxim Tsoi
2
Physics Department, University of Texas at Austin
, Texas 78712, USA
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Leonard F. Register;
Leonard F. Register
1
Microelectronics Research Center, University of Texas at Austin
, Texas 78758, USA
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Sanjay K. Banerjee
Sanjay K. Banerjee
1
Microelectronics Research Center, University of Texas at Austin
, Texas 78758, USA
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J. Appl. Phys. 115, 17D123 (2014)
Article history
Received:
September 23 2013
Accepted:
October 29 2013
Citation
Tanmoy Pramanik, Urmimala Roy, Maxim Tsoi, Leonard F. Register, Sanjay K. Banerjee; Micromagnetic simulations of spin-wave normal modes and the spin-transfer-torque driven magnetization dynamics of a ferromagnetic cross. J. Appl. Phys. 7 May 2014; 115 (17): 17D123. https://doi.org/10.1063/1.4863384
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