CeNi3-type rare earth compounds: crystal structure of R3Co7Al2 (R=Y, Gd–Tm) and magnetic properties of {Gd–Er}3Co7Al2, {Tb, Dy}3Ni8Si and Dy3Co7.68Si1.32

Abstract The crystal structure of new CeNi 3 -type {Y, Gd–Tm} 3 Co 7 Al 2 ( P63/mmc . N 194, hP 24) compounds has been established using powder X-ray diffraction studies. The magnetism of Tb 3 Ni 8 Si and Dy 3 Ni 8 Si is dominated by rare earth sublattice and the magnetic properties of R 3 Co 7 Al 2 ( R =Gd–Er) and Dy 3 Co 7.68 Si 1.32 are determined by both rare earth and cobalt sublattices. Magnetization data indicate ferromagnetic ordering of {Tb, Dy} 3 Ni 8 Si at 32 K and 21 K, respectively. Gd 3 Co 7 Al 2 and Tb 3 Co 7 Al 2 exhibit ferromagnetic ordering at 309 K and 209 K, respectively, whereas Dy 3 Co 7 Al 2 , Ho 3 Co 7 Al 2 , Er 3 Co 7 Al 2 and Dy 3 Co 7.68 Si 1.32 show a field dependent ferromagnetic-like ordering at 166 K, 124 K, 84 K and 226 K, respectively followed by a low temperature transition at 34 K for Dy 3 Co 7 Al 2 , 18 K for Ho 3 Co 7 Al 2 , 56 K for Er 3 Co 7 Al 2 , 155 K and 42 K for Dy 3 Co 7.68 Si 1.32 . Among these compounds, Dy 3 Ni 8 Si shows largest magnetocaloric effect (isothermal magnetic entropy change) of −11.6 J/kg·K at 18 K in field change of 50 kOe, whereas Tb 3 Co 7 Al 2 , Dy 3 Co 7 Al 2 and Dy 3 Co 7.68 Si 1.32 exhibit best permanent magnet properties in the temperature range of 2–5 K with remanent magnetization of 11.95 μ B /fu, 12.86 μ B /fu and 14.4 μ B /fu, respectively and coercive field of 3.0 kOe, 1.9 kOe and 4.4 kOe, respectively.