Structure and magnetocaloric effect of Pr₂Fe_17-xAl_x

Abstract

In this work, we present the results of the substitution of aluminum for iron in Pr₂Fe₁₇. The polycrystalline Pr₂Fe_17-xAl_x samples (x = 0, 0.25, 0.5, 0.75 and 1) were prepared by arc melting under a high purity argon and homogenized at 1373K for one week to minimize the amount of other possible impurity phases. The samples were characterized using powder X ray diffraction (XRD) and were refined using Rietveld method with Full-prof program. The lattice parameters increases with the Al content (from a = 8.5646 Å and c = 12.4394 Å, for x = 0, to a = 8.6194 Å and c = 12.5163 Å, for x = 1) and all the samples crystallize in time R3m of the Th₂Zn₁₇. We can explain this increasing by the largest covalent radius of Al compared to Fe. In addition, we have shown that the Al substitution of Fe increases Tc from 285K (for x = 0) to 361K (for x = 1) due mainly to the magnetovolumic effect. The magnetocaloric effect (MCE) of these compounds has been investigated by measuring their magnetic properties. The magnetic entropy variation decreases slightly from 5.51 Jkg^-1K^-1 to 4.71 Jkg^-1K^-1 under a magnetic field change of 0 - 51.