Structural, magnetic, magnetocaloric and electrical studies of Dy0.5(Sr1−xCax)0.5MnO3 manganites

Abstract

Based on sol-gel method, the Dy0.5(Sr1−xCax)0.5MnO3 (x=0 and 0.3) manganites were synthesized. Orthorhombic distortion was presented in both samples via X-ray diffraction patterns with Pnma as a space group. Magnetic measurements of both systems illustrate anomalies at around TN(Mn)∼27K for the x=0 sample and 40K for x=0.3, showing antiferromagnetic coupling among Mn-spins. Then, the AC magnetic susceptibility of these systems was investigated to demonstrate the existence of spin glass state. In order to check if these samples can be good candidates for magnetic refrigeration, relative cooling power was determined depicting that the sample with a Ca content x=0.3 can be useful for magnetic refrigeration at cryogenic temperatures with about 133.89J/kg under a magnetic field of 5T. The experimental magnetic entropy change was then treated via Landau theory showing a big discrepancy between the measured and the theoretical magnetic entropy change under 1 and 5T. The antiferromagnetic behavior, which is governed by the super exchange interactions, describes also the insulating character, thus, we discussed the electrical properties and examined the conduction mechanisms. Based on Hall effect measurements, charge careers type was determined to be electron for both samples. Eventually, both systems can be investigated also as good candidates for bolometer applications.