Quantum Hall Ferromagnetism in a Two-Dimensional Electron System
J. Eom,1
H. Cho,1
W. Kang,1*
K. L. Campman,2
A. C. Gossard,2
M. Bichler,3
W. Wegscheider34
Experiments on a nearly spin degenerate
two-dimensional electron system reveals unusual hysteretic and
relaxational transport in the fractional quantum Hall effect regime.
The transition between the spin-polarized (with fill fraction 
= 1/3) and spin-unpolarized ( = 2/5) states is accompanied by a
complicated series of hysteresis loops reminiscent of a classical
ferromagnet. In correlation with the hysteresis, magnetoresistance can
either grow or decay logarithmically in time with remarkable
persistence and does not saturate. In contrast to the established
models of relaxation, the relaxation rate exhibits an anomalous
divergence as temperature is reduced. These results indicate the
presence of novel two-dimensional ferromagnetism with a complicated
magnetic domain dynamic.
1 James Franck Institute and Department of
Physics, University of Chicago, Chicago, IL 60637, USA.
2 Department of Electrical Engineering, University
of California at Santa Barbara, Santa Barbara, CA 93106, USA.
3 Walter Schottky Institut, Technische
Universität München, Am Coulombwall, D-85748 Garching,
Germany.
4 University of Regensburg, Regensburg,
Germany.
*
To whom correspondence should be addressed. E-mail:
wkang{at}midway.uchicago.edu
