Large magnetic entropy change in nanocrystalline Pr_(0.7)Sr_(0.3)MnO_3

摘要

Nanocrystalline Pr_(0.7)Sr_(0.3)MnO_3 sample has been prepared by sol-gel method. The room temperature powder x-ray diffraction data show single phase nature of the sample and confirm the cubic crystal structure with Fm3m space group. The average crystallite size is calculated using Scherrer formula, and it is found to be ～25 nm. Transmission electron microscopy image shows that the particles are spherical in shape and the average particle size is ～35 nm. The sample undergoes ferromagnetic ordering at 235 K (T_C) and obeys the Curie-Weiss law in the paramagnetic region. The maximum value of the magnetic entropy change |ΔS_M|_(max) is ～6.3 J kg~(-1) K~(-1), and the relative cooling power is ～385 J kg~(-1) for a field change of 50 kOe. The Arrott plot confirms that the magnetic ordering is of second order nature. The experimentally observed magnetic entropy change of the sample obeys Landau theory of phase transition well.