2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007;
Denver, Colorado
Session S2: Symposium on Exchange Bias
2:30 PM–5:30 PM,
Wednesday, March 7, 2007
Colorado Convention Center
Room: Four Seasons 4
Sponsoring
Unit:
GMAG
Chair: Dan Dahlberg, University of Minnesota
Abstract ID: BAPS.2007.MAR.S2.5
Abstract: S2.00005 : Electric and Magnetic Field control of Exchange Bias*
4:54 PM–5:30 PM
Preview Abstract
Abstract
Author:
Christian Binek
(University of Nebraska-Lincoln)
Exchange bias (EB) and its accompanying training effect are
fundamental
interface phenomena in coupled magnetic thin films with
significant impact
in spintronic applications. Here we report on the electric field
control of
the EB in innovative antiferromagnetic (AF)/ferromagnetic (FM)
heterostructures and the magnetic field control of the EB
training effect in
exchange coupled all FM bilayer systems. Electric control of the
EB is
realized in Cr$_{2}$O$_{3}$ (111)/(Co/Pt)$_{3}$ heterostructures
by taking
advantage of the magnetoelectric (ME) properties of the AF
pinning layer
[1]. An electric field induces excess magnetization in the ME
Cr$_{2}$O$_{3}$ film. Exchange coupling between the induced
magnetization
and the CoPt thin film gives rise to electrically controlled
perpendicular
EB. Bias fields are measured by means of AGFM, SQUID-magnetometry
and polar
Kerr-rotation. Electrically controlled EB is proposed for novel
spintronic
applications such as pure voltage control of magnetic
configurations in spin
valve-type architectures. The latter provide an attractive
alternative to
current-induced switching of the magnetization [2]. In addition,
training of
the EB effect is studied in novel all FM heterostructures of
exchange
coupled soft and hard FM thin films [3]. FM bilayers show remarkable
analogies to the conventional AF/FM EB systems. Not only do they
exhibit a
tunable EB effect, they also show a distinct training behavior
upon cycling
the soft layer through consecutive hysteresis loops. In contrast to
conventional EB systems, all FM bilayers allow the observation of
training
induced changes in the bias-setting hard layer by means of simple
magnetometry. Initialization of the EB is achieved at constant
temperature
exclusively by means of magnetic fields. Our experiments show
unambiguously
that EB training is driven by deviations from the equilibrium spin
configuration of the pinning layer. The experimental data show
excellent
agreement with our theoretical predictions including the subtle
dynamic
enhancement of the EB training which evolves with increasing
field sweep
rates.
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[1] P. Borisov, A. Hochstrat, X. Chen, W. Kleemann, and Ch.
Binek, Phys.
Rev. Lett. 94, 117203 (2005).
\newline
[2] Ch. Binek, B.Doudin, J. Phys. Condens. Matter 17, L39 (2005).
\newline
[3] Ch. Binek, S. Polisetty, Xi He and A. Berger, Phys. Rev.
Lett. 96,
067201 (2006).
*Financial support by NSF through CAREER DMR-0547887, NRI and Nebraska MRSEC.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.MAR.S2.5