Regensburg 2013 – scientific programme
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MA: Fachverband Magnetismus
MA 45: Magnetic Coupling and Spin Structures
MA 45.9: Talk
Thursday, March 14, 2013, 17:15–17:30, H10
Slow magnetic order-order transition in antiferromagnet Ca3Co2O6 — •Stefano Agrestini1, Martin Lees2, Catherine Fleck2, Laurent Chapon3, and Claudio Mazzoli4 — 1Max Planck Institut für Chemische Physik fester Stoffe, Dresden, Germany — 2Physics Department, University of Warwick, Coventry, UK — 3ILL, Grenoble, France — 4Politecnico di Milano, Milano, Italia
Time-dependent phenomena play a crucial role in the properties of many magnetic systems, including spin-glasses, single-molecule magnets and superparamagnets. However time-dependent magnetism is not expected to be observed in the presence of long-range magnetic order. Here we challenge this view by reporting the observation of a new time-dependent behavior where a transition from one long-range magnetically ordered state to another occurs in zero magnetic field over a time scale of several hours. We performed an extensive neutron diffraction study of the spin chain system Ca3Co2O6 whose step-like magnetization versus magnetic field aroused great interest in the scientific community. Our data show that for T< 14K< TN =25K the spin-density-wave order observed immediately below TN, becomes unstable and a commensurate antiferromagnetic phase appears via a very slow transformation process. As the temperature is reduced the characteristic time of the transition process increases rapidly and at low temperatures the magnetic states become frozen. The transition is also noteworthy because the two phases have different propagation vectors. Very rarely transitions between two magnetically ordered phases involve a change of translational symmetry.