Specific heat and magnetocaloric effect in Pr0.6Sr0.4−xAgxMnO3 manganites

The detailed investigation on the specific heat in manganites of Pr0.6Sr0.4−xAgxMnO3 (x=0.05 and x=0.1) has been reported. The experimental conditions were: the temperature range 1.8–330 K and applied magnetic fields of 0, 1, 2 and 3 T. Specific heat results confirmed two phase transitions, a structural one at Tstr = 43 K for both samples and a paramagnetic–ferromagnetic one near TPM–FM=288 K and 284 K for the x=0.05 and x=0.1 sample, respectively. For the more doped sample the magnetic field causes the shift of the PM–FM transition temperature towards higher temperatures. A thorough analysis of particular contributions to the specific heat was presented. The indirect magnetocaloric effect was deduced for the more doped sample (x=0.1). Under anapplied magnetic field of 3 T magnetic entropy changes and adiabatic temperature exhibits a maximum. The absolute ΔSmax reaches the value of 1.74 J/mol K, resulting in adiabatic cooling of ΔTad=0.95 K. Such result onfirms presented samples as promising candidates for the magnetic cooling technology at room temperature

Effect of Ag substitution on structural, magnetic and magnetocaloric properties of Pr0.6Sr0.4– xAgxMnO3 manganites

A systematic investigation on the structural, magnetic and magnetocaloric properties of Pr0.6Sr0.4–xAgxMnO3 (x=0.05 and 0.1) manganites was reported. Rietveld refinements of the X-ray diffraction patterns confirmed that all samples were single phase and crystallized in the orthorhombic structure with Pnma space group. Magnetic measurements in a magnetic applied field of 0.01 T revealed that the ferromagnetic-paramagnetic transition temperature TC decreased from about 293 to 290 K with increasing silver content from x=0.05 to 0.1. The reported magnetocaloric entropy change and relative cooling power for both samples were considerably remarkable with a ΔSmax value of 1.9 J/(kg·K) and maximum RCP values of 100 J/kg, under a magnetic field change (Δµ0H) equal to 1.8 T. The analysis of the universal curves gave an evidence of a second order magnetic transition for the studied samples. The magnetic field influence on both the magnetic entropy change and the relative cooling power was also studied and discussed. © 2017 The Chinese Society of Rare Earth