Macroscopic phase diagram and magnetocaloric study of metamagnetic transitions in the spin chain system Ca3Co2 O6

The magnetic entropy change (ΔSM) 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 ΔSM 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 ΔSM(H) can be found within the ferrimagnetic phase, which are identified with intermediate configurations among the chains. A new magnetic phase diagram has been constructed from the magnetic field and temperature dependence of magnetic entropy change.