Synthesis, structure and magnetic entropy change of polycrystalline La1-xKxMnO3+δ

The use of a sol-gel synthetic method allows the preparation, at temperatures as low as 873 K, of single-phase perovskites in the potassium-doped lanthanide manganites La1-xKxMnO3+delta. Samples prepared at 1273 K remain single phase and are constituted by submicrometer homogeneous particles, without deviation from nominal stoichiometries upon heating. These materials exhibit paramagnetic-to-ferromagnetic phase transitions at 230, 283, 338, and 344 K for x = 0.075, 0.10, 0.165, and 0.20, respectively, By measuring the sample magnetization as a function of held and temperature we have determined the magnetic entropy change associated with these transitions. It is suggested by the results that these materials can be utilized as suitable magnetic refrigerants with very large temperature span. (C) 1999 Elsevier Science B.V. All rights reserved.