2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009;
Pittsburgh, Pennsylvania
Session W32: Focus Session: Theory and Simulation of Spin-Dependent Effects and Properties II
11:15 AM–2:15 PM,
Thursday, March 19, 2009
Room: 336
Sponsoring
Units:
GMAG DCOMP DMP
Chair: Aldo Romero, Cinvestav Querétaro
Abstract ID: BAPS.2009.MAR.W32.4
Abstract: W32.00004 : Current-driven vortex oscillations in metallic nanocontacts
11:51 AM–12:27 PM
Preview Abstract
Abstract
Author:
Gino Hrkac
(University of Sheffield)
In this paper, we performed full micromagnetics simulations of
metallic
nano-contacts from the TUNAMOS consortium, by solving the Landau
Lifshitz
Gilbert Slonctewski equation simultaneously with quasi-static
Maxwell
equations. We take into account the spatially inhomogeneous current
distribution flowing through the magnetic free layer and
consequently use
the Oersted field generated by this current for the magnetization
dynamics.
The system we simulated was a trilayer CoFe 3$.$5 nm/Cu 3nm/NiFe
4nm stack. The
saturation magnetization of the free layer is taken to be the
same as the
experimental value \textit{Ms }=1$.$1 T, and a GMR ratio of 1{\%}
is used. We account for
the inhomogeneous current distribution flowing through the free
layer by
computing the local current density from the local angle between
the free
and fixed layer magnetizations. The Oersted field is computed
with the
Biot-Savart law from this current distribution [2], and an
asymmetric
Slonczewski term for the spin transfer is used [3].
We observe that the additional spin torque drives the vortex out
of the
contact area and towards a stable orbit around the contact. These
simulations reveal that the oscillations observed are related to the
large-amplitude translational motion of a magnetic vortex. In
contrast to
the nanopillar geometry in which the vortex core precesses within
the
confining part of the Oersted field [1], the dynamics here
correspond to an
orbital motion \textit{outside }the contact region. This behavior
can be likened to planetary
orbital motion under the influence of a gravitational field; the
spin-transfer torque leads to a centripetal motion of the vortex
core, which
is counterbalanced by the attractive potential provided by the
Oersted
field. Good quantitative agreement between the simulation and
experimental
frequencies is achieved [4].
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[1] V. S. Pribiag et al., Nat. Phys. \textbf{3}, 498 (2007)
\\[0pt]
[2] O. Ertl \textit{et al.}, J. Appl. Phys. \textbf{99}, 08S303
(2006).
\\[0pt]
[3] J. Xiao, A. Zangwill, and M. D. Stiles, Phys. Rev. B
\textbf{70}, 172405
(2004).
\\[0pt]
[4] Q. Mistral, M. van Kampen, G. Hrkac, et al. PRL \textbf{100,
}257201 (2008)
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.MAR.W32.4