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

The magnetic ordering of Nd, Fe,, Sn and Pr,Fe,, Sn powder samples was inve stigated by neutron diffraction. The data analysis reveals a collinear anti ferromagnetic magnetic moment arrangement of the four Fe and the two R subl attices associated with the wave Vector q = (0 0 1) corresponding to the I- p magnetic lattice with anticentering translation. The moments of all subla ttices located at (x y 0) layers, sandwiched between successive Sn layers p erpendicular to z at z = - 0.25, 0.25 are confined to the same direction. T hese 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 Pr,Fe,,Sn compound. For the Nd, Fe,, Sn compound it is along the c-axis for T > 150 K and 10 degrees off the c- axis at 1.5 K. The moment values of the R atoms at 1.5 K are 3.06(7)mu(B) a nd 2.45(4)mu(B),/Nd atom 2.9(1)mu(B) and 2.70(1)mu(B)/Pr atom while the ave rage Value of the ordered Fe moment is 2.4 mu(B)/Fe for both compounds, in satisfactory agreement with Mossbauer results. (C) 2000 Elsevier Science B. V. All rights reserved.