Low-Temperature Heat Capacity of $$\hbox {Sr}_2\hbox {Ca}_{12}\hbox {Cu}_{24}\hbox {O}_{41}$$Sr2Ca12Cu24O41

We report on heat capacity measurements performed on a large Sr2Ca12Cu24O41 single crystal in the temperature range between 0.07 and 20 K and magnetic fields up to 10 T. A transition into the antiferromagnetic ground state is observed at TN=2.8 K. The heat capacity becomes strongly time-dependent below 0.5 K due to a Schottky contribution typical for materials with charge or spin-density waves. We found a quasi-linear contribution to the heat capacity that can be attributed to weakly coupled and shifted antiferromagnetic spin chains along the a-direction.