Excellent cooling power in chemically compressed double layer Ruddlesden-Popper ceramics La1.4-xNdxSr1.6Mn2O7 (0.0 ≤ x ≤ 0.15)

Here we report, structural, microstructural and magnetocaloric characteristics of double layer ceramics La1.4-xNdxSr1.6Mn2O7, upon Nd-modification (0.0 <= x <= 0.15). Initially, the bulk specimens were produced through solid-state sintering route and the Ruddlesden-Popper (R-P) structure with tetragonal symmetry was identified from X-ray diffraction (XRD) data. Along with the R-P phase the hexagonal perovskite phase was intermittently formed during the sintering process. The specimens with x = 0.0 and x = 0.1 stoichiometry contained the lowest amounts of perovskite phase (<= 3.5%) whereas the fraction was raised (<= 6%) in x = 0.05 and x = 0.15 compositions. Inspection of the refined structure disclosed that the unit cell parameters were regularly decreased with respect to Nd-concentration which facilitated the compression of unit cell volume. The electron microscopic (SEM) analysis of the microstructure revealed a uniform distribution of grains, the average grain size and density was enhanced upon raising the Nd-concentration. The magnetic response against variable magnetic field (M - H) and temperature (M-T) was maximum for x = 0.0 and x = 0.1 samples, magnetization was reduced in the rest of compositions. Moreover, multiple magnetic transitions were observed across the temperature axis in M-T curves, which indicated the presence of local magnetic clusters in the samples. The highest change in the magnetic entropy (Delta S-M) = 2.32 Jkg(-1)K(-1) was achieved with 2.5 T magnetic field, for x = 0.1 sample. Moreover, temperature averaged change in the magnetic entropy (TEC) of prepared manganites was surprisingly robust between the thermal boundaries (Delta TH-C) = 5 K-20 K of the heat exchanger. Lastly, the relative cooling power greatly improved from 91.54 J/kg to 96.74 J/kg, 105.90 J/kg and 109.43 J/kg for x = 0.00, 0.05 and 0.1 and 0.15 concentrations of Nd.