Neutron diffraction study of RMn4Al8 (R=Nd, Dy, Ho, Er), ErCr4Al8 and ErCu4Al8

Neutron powder diffraction has been used to investigate the magnetic order in a series of RMn(4)Al(8) (space group I-4/mmm) compounds with R = (Nd, Dy, Ho and Er). For compounds with Mn, no magnetic order was detected down to 1.6K, whilst for the compound ErCr4Al8, two very weak magnetic reflections were observed at 1.6 K. The observed magnetic peaks cannot be indexed on the tetragonal unit cell, indicating a possible incommensurate magnetic structure. For ErCu4Al8, a type 1 antiferromagnetic structure is observed. The magnitude and temperature dependence of the Er3+ magnetic moment can be adequately modelled by a combined isotropic exchange and tetragonal crystal held Hamiltonian within the Mean Field Approximation.