Incommensurate magnetic structure and its long-time variation in a geometrically frustrated magnet Ca3Co2O6

Magnetization and neutron scattering measurements have been performed on a single crystal of the magnetically frustrated compound Ca3Co2O6. This compound has no random magnetic interactions, but has frustrating magnetic interactions arising from its crystal structure. In this material, a long-time variation in magnetic structure has been observed. After cooling the sample below the transition temperature Tc2=13 K, the magnetic Bragg peaks at (1, 0, ±δ) corresponding to an incommensurate antiferromagnetic structure move toward (1, 0, 0) with time. The characteristic time for this variation follows the Arrhenius law with an activation energy Ea/kB-53 K. A new magnetic structure model of this material is also presented. (author)