Magnetic and magnetocaloric properties of R6Mn23 (R=Y, Nd, Sm, Gd-Tm, Lu) compounds

The magnetic and magnetocaloric properties of the R₆Mn₂₃ compounds (R=Y, Nd, Sm, Gd-Tm, Lu) are investigated from DC magnetization measurements. The results are analyzed and discussed in connection with previously published data. These binaries crystallize in the cubic Th₆Mn₂₃ type of structure (Fm-3m). The Mn sublattice orders at high temperature (398 K≤T_C≤505 K) with a collinear ferrimagnetic structure. The R sublattice orders at lower temperature (<100 K) with a non-collinear arrangement. By opposition with the usual behaviour in intermetallics, light rare-earth compounds (R=Nd and Sm) have a lower ground state magnetization than the heavy rare-earth compounds (R=Gd-Tm). This manifests in their magnetocaloric response near the R ordering temperature: the compounds with R=Gd-Tm display a normal magnetocaloric effect of moderate magnitude (<50 mJ cm⁻³ K⁻¹ for a field variation of 5 T) while those with R=Nd and Sm present an inverse magnetocaloric effect of weaker magnitude. The potential interest of these phases for cooling applications is briefly discussed.