Structural anomaly in GdNiAl: a crystallographic, electric and magnetic investigation

Low temperature electrical resistivity and X-ray powder diffraction measurements showed a transformation paint at about 200 K, attributed to a transition between two slightly different crystallographic forms of the ZrNiAl type. A corresponding anomaly was observed in the thermal behaviour of the magnetic susceptibility, and the results were analyzed in the framework of the RKKY theory. Ferromagnetic ordering occurs at 57 K, and two other transition temperatures, 30 and 14 K, were detected: these points, as already observed for TbNiAl, DyNiAl and HoNiAl may be imputed to order-order magnetic transitions