2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009;
Pittsburgh, Pennsylvania
Session X31: Focus Session: Magnetic Nanostructures: Domain Walls, Reversal, Oscillators
2:30 PM–5:06 PM,
Thursday, March 19, 2009
Room: 335
Sponsoring
Units:
DMP GMAG
Chair: Valnetyn Novosad, Argonne National Laboratory
Abstract ID: BAPS.2009.MAR.X31.1
Abstract: X31.00001 : Reversal mechanisms and defects in perpendicularly magnetized nanostructures
2:30 PM–3:06 PM
Preview Abstract
Abstract
Author:
Justin Shaw
(NIST)
The problem of switching field distributions (SFDs) is
currently plaguing developing technologies which rely on
uniform arrays of magnetic nanostructures such as bit patterned
media, magnetic random access memory (MRAM) and spin-torque
oscillators. Most of these technologies are shifting towards
the use of perpendicularly magnetized materials due to the
increased device performance and thermal stability that can be
achieved. SFDs in such perpendicularly magnetized
nanostructures can result from dot-to-dot interactions and size
distribution, but is largely dominated by material defects [1-
4]. Such defects can arise from both the material deposition
process, and post-deposition processing that occurs during
nanofabrication. By comparing nanostructures fabricated by
deposition on pre-patterned wafers to those fabricated by ion
milling of continuous films, we show that the anisotropy of the
edge region can be greatly different in each case. The size,
temperature, and angular dependences of the reversal field
indicate that the reversal mechanism also differs. In contrast
to fabrication induced defects, microstructural variations
manifest themselves as a random distribution of local
anisotropies. We studied the anisotropy distribution in
patterned elements by imaging the localized reversal of low
anisotropy regions and mapping these sites as a function of
applied field using MFM imaging and TEM. In addition, we used
simulations to show the effect a small localized region of
lower anisotropy material (such as a grain) has on the reversal
field of the entire nanostructure. We find that the reversal
field depends on both the relative anisotropy of the defect to
the film, as well as, the location of the defect within the
structure. \\[4pt]
[1] T. Thomson, PRL 96,257204 (2006).\\[0pt]
[2] J.M. Shaw, JAP 101, 023909 (2007).\\[0pt]
[3] J. Lau, APL 92, 012506 (2008).\\[0pt]
[4] J.M. Shaw, PRB 78, 024414 (2008).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.MAR.X31.1