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Field  dependence of the refrigerant capacity for La-based manganites

Ritta Szymczak 1Roman Kolano 2Aleksandra Kolano-Burian 2Roman Puzniak 1Henryk Szymczak 1

1. Polish Academy of Sciences, Institute of Physics, Warszawa 02-668, Poland
2. Institute of Nonferrous Metals, Sowińskiego 5, Gliwice 44-100, Poland


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 | ΔSM  | 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 | ΔSM  | or the refrigerant capacity (RC) is used. The refrigerant capacity is defined as RC = ΔSM 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 La1-xCax MnO (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 ~ Hα. 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


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Presentation: Poster at E-MRS Fall Meeting 2008, Symposium C, by Henryk Szymczak
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-18 10:22
Revised:   2009-06-07 00:48