Magnetic dynamics across the in-field transition in Ca_3Co_2O_6

摘要

The discovery of multiple coexisting magnetic phases in the crystallographically homogeneous compound Ca_3Co_2O_6 has stimulated ongoing research activity. In recent years the main focus has been on the zero-field-state properties, where exceedingly long timescales have been established. In this study we report a detailed investigation of static and dynamic properties of Ca_3Co_2O_6 across the magnetic field induced transition around 3.5 T. This region has so far been practically neglected, while we argue that in some aspects it represents a simpler version of the transition across the B = 0 state. Investigating the frequency dependence of the ac susceptibility, we reveal that on the high-field side (B > 3.5 T) the response corresponds to a relatively narrow distribution of magnetic clusters. The distribution appears very weakly dependent on magnetic field, with an associated energy barrier of around 200 K. Below 3.5 T a second contribution arises, with much smaller characteristic frequencies and a strong temperature and magnetic field dependence. We discuss these findings in the context of intrachain and interchain clustering of magnetic moments.