  We have investigated the magnetocaloric effects in antiferromagnets and
compared them with those in ferromagnets using Monte Carlo simulations. In
antiferromagnets, the magnetic entropy reaches a maximum value at a finite
magnetic field when the temperature is fixed below the N\'eel temperature.
Using the fact, we proposed a protocol for applying magnetic fields to achieve
the maximum efficiency for magnetic refrigeration in antiferromagnets. In
particular, we found that at low temperatures, antiferromagnets are more useful
for magnetic refrigeration than ferromagnets.
