Low-Frequency Spin Dynamics in a Canted Antiferromagnet
Norio Kumada,1*
Koji Muraki,1
Yoshiro Hirayama1,2,3
Resistively detected nuclear spin relaxation measurements in
closely separated two-dimensional electron systems reveal strong
low-frequency electron-spin fluctuations in the quantum Hall
regime. As the temperature is decreased, the spin fluctuations,
manifested by a sharp enhancement of the nuclear spin-lattice
relaxation rate 1/
T1, continue to grow down to the lowest temperature
of 66 millikelvin. The observed divergent behavior of 1/
T1 signals
a gapless spin excitation mode and is a hallmark of canted antiferromagnetic
order. Our data demonstrate the realization of a two-dimensional
system with planar broken symmetry, in which fluctuations do
not freeze out when approaching the zero temperature limit.
2 SORST–Japan Science and Technology Agency, 4-1-8 Honmachi, Kawaguchi, Saitama 331-0012, Japan.
3 Department of Physics, Tohoku University, Sendai 980-8578, Japan.
* To whom correspondence should be addressed. E-mail: kumada{at}will.brl.ntt.co.jp
