Specific heat of phase-separated (La0.7-2xEux)(Ca0.3Srx)MnO3 (x=0.15, 0.20 and 0.25) manganite compounds

The specific heat measurements have been performed on three manganite compounds (La0.7-2xEux)(Ca0.3Srx)MnO3 (x = 0.15, 0.20 and 0.25) having different magnetic ground states. For ferromagnetic (FM) x = 0.15 compound, an anomaly in the specific heat (C-p) with an entropy change of similar to 1.4-1.8 J/mol K occurs at the ferromagnetic transition in zero as well as applied magnetic fields. In the phase-separated x = 0.20 compound, no feature is observed in C-p corresponding to antiferromagnetic (AFM) to FM-phase transition at 75 K in zeromagnetic field. Interestingly, this compound shows a peak-like anomaly in Cp with an entropy change of similar to 1.4 J/mol K at an elevated temperature of 110K in a field of 5T. Combining these features with magnetization data, we show that the thermal anomaly in x = 0.20 sample arises from paramagnetic to FM-phase transition and not from AFM- to FM-phase transition. A similar anomaly occurs in x = 0.25 compound in a field of 9T, but with a small entropy change of 0.5J/mol K that agrees well with its field-induced FM-phase fraction. (c) 2006 Elsevier B.V. All rights reserved.