Magnetic ordering of the R6Fe13Sn (R=Nd, Pr) compounds studied by neutron diffraction

The magnetic ordering of Nd6Fe13Sn and Pr6Fe13Sn powder samples was investigated by neutron diffraction. The data analysis reveals a collinear antiferromagnetic magnetic moment arrangement of the four Fe and the two R sublattices associated with the wave vector q=(0 0 1) corresponding to the IP magnetic lattice with anticentering translation. The moments of all sublattices located at (x y 0) layers, sandwiched between successive Sn layers perpendicular to z at z= -0.25, 0.25 are confined to the same direction. These ferromagnetic blocks change their direction collectively when going to the next Sn layers at z=0.25, 0.75. The structures of the two compounds differ essentially in the preferred direction of antiferromagnetism, which is perpendicular to the c-axis for the Pr6Fe13Sn compound. For the Nd6Fe13Sn compound it is along the c-axis for T>150 K and 10 deg. off the c-axis at 1.5 K. The moment values of the R atoms at 1.5 K are 3.06(7) μB and 2.45(4) μB/Nd atom 2.9(1) μB and 2.70(1) μB/Pr atom while the average value of the ordered Fe moment is 2.4 μB/Fe for both compounds, in satisfactory agreement with Moessbauer results