In recent years, there has been increasing interest in using manganities not only as material having colossal magnetoresistivity but also as material having promising magnetocaloric properties.  A large magnetocaloric effect makes manganities excellent candidate for working materials in magnetic refrigeration units especially because these are less costly than any other materials, particularly materials based on gadolinium. Moreover, we have shown that the magnetic entropy change | ΔS_M  | in La-based manganites is larger than that exhibited by gadolinium. In order to compare existing magnetic refrigerant materials, either the peak of magnetic entropy change | ΔS_M  | or the refrigerant capacity (RC) is used. The refrigerant capacity is defined as RC = ΔS_M ΔT, where  ΔT is the operating temperature range of the cycle. The optimal refrigeration cycle is that which maximizes of RC. We present the results of RC measurements on La_1-xCa_x MnO₃  (x = 0.5-0.7) polycrystalline manganites in magnetic fields up to 9T.The maximum of RC is larger than that of gadolinium measured under the same experimental conditions It was shown that the refrigerant capacity for manganites can be expressed as RC ~ H^α. The field  dependence of the  refrigerant capacity was analyzed in frames of scaling model, showing a power dependence related  directly to critical exponents in agreement with experiment..

This work  is party supported by the Ministry of Science and Higher Education of Poland Project PBZ-KBN-115/T08/2004