Magnetic and magnetocaloric properties of the new R3Co4+xAl12-x (R: Tb → Er) with the Gd3Ru4Al12 structure-type

The novel intermetallics R3Co4,Al-12 (R = Tb -> Er) crystallize in the hexagonal Gd3Ru4Al12 structure-type where the rare earth atoms form a heavily distorted kagome network. Single crystal X-ray diffraction reveals an unusual 2b substitution site of Co for Al probably driven by steric effects. The four phases order ferromagnetically below 24.0, 17.4, 11.5 and 5.0 K for R = Tb, Dy, Ho and Er, respectively, linearly decreasing with the de Gennes factor of the rare earth. The magnetocaloric properties have been estimated for R = Ho and Er by measuring the magnetization isotherms at various temperatures. The magnetic entropy changes reach maximum values of -12 and -10 J kg(-1) k(-1) for a magnetic field change from 5 to 0 T.