Macroscopic phase diagram and magnetocaloric study of metamagnetic transitions in the spin chain system Ca3Co2O6

The magnetic entropy change ( SM) in a single crystal of the geometrically frustrated spin chain system Ca3Co2O6 has been determined under the influence of a wide range of temperatures and magnetic field variations. Our findings are consistent with the spin-density wave description of the zero field order, and with the suppression of the modulated state at low field. Metamagnetic transitions to the ferrimagnetic up-up-down configuration and full ferromagnetic alignment are observed upon the application of moderate magnetic fields in the c direction. At low temperatures, an increase in SM supports the presence of short-range magnetic correlations coexisting with long-range order up to large fields. Depending on the temperature regime, local maxima or minima in SM(H ) can be found within the ferrimagnetic phase, which are identified with intermediate configurations among the chains. A newmagnetic phase diagram has been constructed from the magnetic field and temperature dependence of magnetic entropy change.