| 초록 |
In this work we have prepared a series of self-doped Pr1.4-xSr1.6-xMn2O7 (0.0 ≤ x ≤ 0.5) double layer manganites from the solid-state reaction method. The structural and magnetic properties were investigated and finally the room temperature magnetocaloric response has been enhanced. The X-ray diffraction profiles revealed that the samples exhibit Ruddlesden-Popper bilayer phase consisting the tetragonal symmetry in all the samples. With increasing the Pr-concentrations the tetragonal symmetry reduces to the single perovskite phase (orthorhombic) and additional PrO2/Pr(OH)3 phases were also emerged. The fractions of each phases were calculated from the Rietveld refinement method and their effects on the magnetic and magnetocaloric properties were analyzed. We found that the total magnetization increases with increasing the Pr-content, which indicates that the incorporation of Pr3+ alters the Mn3+/Mn4+ ratio thereby enhancing the double exchange ferromagnetic coupling. Even so, the change in magnetic entropy at 300 K was significantly enhanced from 0.28 J.kg-1.K-1 (x = 0.0) upto 0.9 J.kg-1.K-1 (x = 0.5) at an applied field of 2.5 T. Similarly, the relative cooling power of 28 J/kg, 35 J/kg, 51 J/kg, 65 J/kg, 74 J/kg, 78 J/kg for 0.0, 0.1 0.2, 0.3, 0.4, 0.5 respectively was achieved under the magnetic field of 2.5 T. Our findings in this work advocates enormous cooling potential of Pr1.4-xSr1.6-xMn2O7 double layer manganites. Moreover, by controlling the phase compositions and experimental set-up, their cooling capacity can be further enhanced for room temperature refrigeration applications.
|
