Magnetic contributions to the specific heat of La0.8Ca0.2Mn1-xCoxO3 perovskite

• Co-doped LaCa-based manganites were synthesized by sol-gel method.
• Magnetic cooling efficiency suitable for magnetic refrigeration was observed.
• MCE evaluated from specific heat was higher than from magnetization measurements.
• Co-substitution induced a change from first order to second order magnetic transition.
• The un-doped manganite revealed tri-critical behavior.

La0.8Ca0.2Mn1-xCoxO3 compounds with x = 0.0, 0.1, 0.2, and 0.3 were synthesized by sol–gel method and their structures characterized by Rietveld refinement of their powder x-ray diffraction patterns. The magnetocaloric effect of these compounds was investigated by means of specific heat measurements as a function of applied magnetic field. The zero-field specific-heat anomaly at the ferromagnetic-paramagnetic phase transition temperature broadened and reduced with increasing the Co content in the samples, resulting in broadening of the magnetocaloric parameter curves. The magnetic entropy change and the adiabatic temperature change were evaluated, and the observed behaviour was consistent with thermodynamic expectations. The change of the adiabatic temperature deduced from specific heat measurements were compared with those obtained from the indirect magnetization measurements method. Relatively high magnetic entropy change and adiabatic temperature change were observed, indicating that these compounds are potential magnetic refrigerants in the sub-room temperature regime.

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