Magnetic structure study of ErCuAl and ErNiAl

Polycrystalline samples of ErCuAl and ErNiAl have been studied by powder neutron diffraction and, in the case of ErCuAl, by specific heat and AC-susceptibility measurements, ErCuAl orders ferromagnetically with Er magnetic moments aligned along the c-axis below T-c=6.8 K. In the case of ErNiAl, magnetic ordering below T-N=5.4 K and indications of an additional phase transition at 4.2 K have been observed. The magnetic structure of ErNiAl is described by the propagation vector (1/2 0 1/2). The magnetic moments lie in the basal plane at 1.8 K.