Structural and magnetic properties with large reversible magnetocaloric effect in (La_1-xPr_x)_0.85Ag_0.15MnO₃ (0.0 ≤ x ≤ 0.5) compounds

Abstract

We report on the effect of Pr doping on structural, magnetic and magnetocaloric properties in (La_1−xPr_x)_0.85Ag_0.15MnO₃ (0.0 ≤ x ≤ 0.5) compounds. The main crystal structure has been studied by performing X-ray diffraction method and structural analysis based on Rietveld method where it is found that although samples at low concentration level (x ≤ 0.2) have rhombohedral phase , others (x ≥ 0.3) have orthorhombic (Pbnm) phase. Scanning electron microscope images show that the average particle size decreases by increasing Pr amount in the main structure. It is observed that the second-order transition temperature from ferromagnetic to paramagnetic phase is dramatically decreased from 262 to 138 K by increasing Pr concentration in (La_1−xPr_x)_0.85Ag_0.15MnO₃. On the other hand, all samples have also antiferromagnetic coupling observed below T_N ~ 50 K. The maximum magnetic entropy change (−ΔS_M)_max and relative cooling power values were found in the range of 7.90–2.88 J/kg K and 213.32–153.50 J/kg, respectively, under 50 kOe field change in our samples. It can be argued that particularly the compounds LPAM with x = 0.0, 0.1 and 0.2 are expected to be promising candidate for magnetic refrigeration.

Keywords:

• Manganites
• sol-gel
• magnetic entropy change
• magnetocaloric effect

Acknowledgements

The authors thank Dr. Deniz Takcı for his technical assistance in XRD measurements. The authors also thank Selda Kılıç Çetin and Gönül Akça for their helpful discussions.

Funding

This work was supported by the Çukurova University, Adana, Turkey [grant contract number FBA-2015-5028], [grant contract number FEF2010D11].