  Large magnetocaloric effect has been observed in Mn3O4 around its
ferrimagnetic transition at TN = 42.75 K. Field-induced isothermal entropy
changes (\DeltaS) were derived from both magnetic and calorimetric techniques.
The maximum |\DeltaS| and adiabatic temperature change ({\Delta}Tad) at TN are
11 J kg-1 K-1 and 1.9 K, respectively, for a magnetic field change of 20 kOe.
Moreover, it is found that the complex magnetic phase transitions taking place
below TN produce additional -but smaller- features on \DeltaS(T).
