New RNiSn4 compounds (R=rare earth): crystal structure of new LuNiSn4 type, magnetic and transport properties

A series of new RNiSn4 compounds (R=Gd–Tm, Lu) has been synthesized. The crystal structure of LuNiSn4 has been determined. It is a new structure type, described as a commensurate modulated structure with space group Ammm/(ddd) and lattice parameters a=4.386 ?, b=27.942 ? and c=4.353 ?. The other investigated compounds have the same structure. Magnetization was measured in the temperature range 1.5–300 K, and, except for the Dy compound, the resistivity was studied between 4 and 300 K. Moreover, the specific heat of the Er and Lu compounds was studied between 1.2 and 30 K. All compounds with magnetic rare earths order antiferromagnetically below their Néel temperature, which ranges from 3 K (R=Tm) to 27 K (R=Gd). Below TN, metamagnetic transitions are observed. In the compound with Er, the specific heat reveals that, immediately below TN=8.8 K, there is a second transition at 8.5 K. The intermediate phase is likely a modulated structure.