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 cr ystal 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 Angstrom, b=27.942 Angstrom and c=4.353 An gstrom. The other investigated compounds have the same structure. Magnetiza tion was measured in the temperature range 1.5-300 K, and, except for the D y 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 t heir Neel temperature, which ranges from 3 K (R-Tm) to 27 It (R=Gd). Below T-N, metamagnetic transitions are observed. In the compound with Er, the sp ecific heat reveals that, immediately below T-N=8.8 K, there is a second tr ansition at 8.5 K. The intermediate phase is likely a modulated structure. (C) 2000 Elsevier Science S.A. All rights reserved.