Origin of Magnetization Decay in Spin-Dependent Tunnel Junctions
Martha R. McCartney,
1*
Rafal E. Dunin-Borkowski,
1
Michael R. Scheinfein,
2
David J. Smith,
12
Savas Gider,
3
Stuart S. P. Parkin
3
Spin-dependent tunnel junctions based on magnetically hard and soft
ferromagnetic layers separated by a thin insulating barrier have
emerged as prime candidates for information storage. However, the
observed instability of the magnetically hard reference layer, leading
to magnetization decay during field cycling of the adjacent soft layer,
is a serious concern for future device applications. Using Lorentz
electron microscopy and micromagnetic simulations, the hard-layer decay
was found to result from large fringing fields surrounding magnetic
domain walls in the magnetically soft layer. The formation and motion
of these walls causes statistical flipping of magnetic moments in
randomly oriented grains of the hard layer, with a progressive trend
toward disorder and eventual demagnetization.
1 Center for Solid State Science,
2 Department of Physics and Astronomy, Arizona State
University, Tempe, AZ 85287-1704, USA.
3 IBM
Almaden Research Center, 650 Harry Road, San Jose, CA 95120-6099, USA.
*
To whom correspondence should be addressed. E-mail:
molly.mccartney{at}asu.edu.
Present address: Department of Materials, University
of Oxford, Parks Road, Oxford OX1 3PH, UK.
