  Solid state-refrigerants have generated worldwide interest owing to their
growing potential for use in efficient and green cooling devices. Caloric
effects could be obtained by manipulating their degrees of freedom such as
magnetization, electric polarization and volume using a variable external
field. In conventional magnetocaloric refrigeration systems, the magnetocaloric
effect is exploited by moving the active material in and out of the magnetic
field source. Here we demonstrate that a giant and reversible magnetocaloric
effect can be generated simply by rotating the multiferroic TbMn2O5 single
crystal around its b axis in a relatively low constant magnetic field applied
in the ac plane. For a magnetic field applied along the easy axis a, we report
an entropy change of 12.25 J/kg K at about 10 K in a field change of 5 T which
is 100 times larger than that found when the field is applied along the hard
axis c. When the TbMn2O5 is rotated with the field remaining in the ac plane,
the associated adiabatic temperature change reaches minimum values of 8 K and
14 K under 2 T and 5 T, respectively. This giant rotating magnetocaloric effect
in TbMn2O5 is caused by the colossal anisotropy of the entropy change, the
enhancement of the magnetization under relatively moderate magnetic fields and
the lower magnitude of specific heat. On the other hand, the application of the
coherent rotational model demonstrates that the rotating magnetocaloric effect
exhibited by TbMn2O5 does not originate directly from the magneto-crystalline
anisotropy. Our results should inspire and open new ways toward the
implementation of compact, efficient and embedded magnetocaloric devices for
low temperature and space application. Its potential operating temperature
range of 2 to 30 K makes it a great candidate for the liquefaction of hydrogen.
