Magnetic ordering of Pr6F13Si and Nd6Fe13Au studied by neutron diffraction

The magnetic structure of the compounds Pr6Fe13Si and Nd6Fe13Au has been st udied by powder neutron diffraction. The magnetic structures are very simil ar, revealing the same collinear antiferromagnetic ordering of the Fe (four ) and the R (two) sublattices associated with the wavevector q = (001) and an I-P type magnetic lattice with anticentring translation. The moments of all sublattices located in (xyo) layers and sandwiched between successive S i (Au) layers perpendicular to z at z = -0.25, 0.25, are confined to the sa me direction within the (xyo) plane. They change their direction collective ly when going to the next Au (Si) layers at z = 0.25, 0.75, thus producing antiferromagnetic ordering within all eight sublattices. At 1.5 K, the rare earth moments in Nd6Fe13Au are equal to 3.4(2) mu(B) for Nd1 and 2.5(1) mu (B) for Nd2. In Pr6Fe13Si the two Pr sites have almost the same moment of 2 .8(1) mu(B) at 1.5 K. The average ordered Fe moment value is lower in Pr6Fe 13Si (1.57 mu(B)/Fe atom) than in Nd6Fe13Au (2.3 mu B/Fe atom).