  We explore the low-energy regime of quantum chromodynamics subjected to an
external magnetic field by deriving the two-loop representations for the
entropy density and the magnetization within chiral perturbation theory (CHPT).
At fixed temperature, the entropy density drops when the magnetic field becomes
stronger. The magnetization induced at finite temperature is negative in the
entire parameter region accessible by CHPT. We also point out that the
enhancement of the finite-temperature part in the quark condensate is
correlated with the decrease of the entropy density.
