title: Low-frequency spin dynamics in a canted antiferromagnet.
abstract: 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.
authors.affiliation: NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan. kumada@will.brl.ntt.co.jp
authors.forename: Norio
authors.initials: N
authors.lastname: Kumada
authors.forename: Koji
authors.initials: K
authors.lastname: Muraki
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Hirayama