title: Statics and dynamics of incommensurate spin order in a geometrically frustrated antiferromagnet CdCr2O4.
abstract: Using elastic and inelastic neutron scattering we show that a cubic spinel, CdCr2O4, undergoes an elongation along the c axis (c > a = b) at its spin-Peierls-like phase transition at T(N) = 7.8 K. The Néel phase (T < T(N)) has an incommensurate spin structure with a characteristic wave vector Q(M) = (0, delta,1) with delta approximately 0.09 and with spins lying on the ac plane. This is in stark contrast to another well-known Cr-based spinel, ZnCr2O4, that undergoes a c-axis contraction and a commensurate spin order. The magnetic excitation of the incommensurate Néel state has a weak anisotropy gap of 0.6 meV and it consists of at least three bands extending up to 5 meV.
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8552, USA.
authors.forename: J-H
authors.initials: JH
authors.lastname: Chung
authors.forename: M
authors.initials: M
authors.lastname: Matsuda
authors.forename: S-H
authors.initials: SH
authors.lastname: Lee
authors.forename: K
authors.initials: K
authors.lastname: Kakurai
authors.forename: H
authors.initials: H
authors.lastname: Ueda
authors.forename: T J
authors.initials: TJ
authors.lastname: Sato
authors.forename: H
authors.initials: H
authors.lastname: Takagi
authors.forename: K-P
authors.initials: KP
authors.lastname: Hong
authors.forename: S
authors.initials: S
authors.lastname: Park