The magnetic and crystallographic properties of induction-melted NdMn(6−x)FexGe6 intermetallics (x=0, 1.0, and 1.5) in the temperature range of 30–475 K have been studied by x-ray and neutron diffraction techniques and SQUID measurements. All of the samples crystallized in the YCo6Ge6-type structure (P6/mmm). A small amount (<5 mol%) of Nd(MnFe)2Ge2 is present as an impurity. As expected, iron replaces manganese at the 3g site. The unit cell volume decreases slightly with increasing iron content at an average rate of 1.3% per substituted atom. Lattice parameters a and c contract at a rate of 0.6% and 0.2% per substitution atom, respectively. The net magnetization of these samples decreases rapidly with increasing iron content. According to neutron diffraction data, the magnetic moment of the iron sublattice couples negatively with ferromagnetically coupled manganese and neodymium moments. Addition of iron suppresses the spin reorientation processes observed in NdMn6Ge6. Whereas the net moment in NdMn5Fe1Ge6 slowly cants away from the c-axis with increasing temperature, the easy direction of NdMn4.5Fe1.5Ge6 is approximately parallel to the c-axis in the temperature range mentioned above.
Han, J., Marasinghe, G. K., James, W. J., Chen, M., Yelon, W. B., Dubenko, I. and Ali, N.. "The Atomic and Magnetic Structure of NdMn(6−x)FexGe6 Solid Solutions." (May 2000).