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 CeNi3-type {Y, Gd–Tm}3Co7Al2 (P63/mmc. N 194, hP24) compounds has been established using powder X-ray diffraction studies. The magnetism of Tb3Ni8Si and Dy3Ni8Si is dominated by rare earth sublattice and the magnetic properties of R3Co7Al2 (R =Gd–Er) and Dy3Co7.68Si1.32 are determined by both rare earth and cobalt sublattices. Magnetization data indicate ferromagnetic ordering of {Tb, Dy}3Ni8Si at 32K and 21K, respectively. Gd3Co7Al2 and Tb3Co7Al2 exhibit ferromagnetic ordering at 309K and 209K, respectively, whereas Dy3Co7Al2, Ho3Co7Al2, Er3Co7Al2 and Dy3Co7.68Si1.32 show a field dependent ferromagnetic-like ordering at 166K, 124K, 84K and 226K, respectively followed by a low temperature transition at 34K for Dy3Co7Al2, 18K for Ho3Co7Al2, 56K for Er3Co7Al2, 155K and 42K for Dy3Co7.68Si1.32. Among these compounds, Dy3Ni8Si shows largest magnetocaloric effect (isothermal magnetic entropy change) of −11.6J/kg·K at 18K in field change of 50kOe, whereas Tb3Co7Al2, Dy3Co7Al2 and Dy3Co7.68Si1.32 exhibit best permanent magnet properties in the temperature range of 2–5K with remanent magnetization of 11.95 μB/fu, 12.86 μB/fu and 14.4 μB/fu, respectively and coercive field of 3.0kOe, 1.9kOe and 4.4kOe, respectively.