Crystallographic and magnetic structures of Pr₆Fe₁₃Ge studied by powder neutron diffraction

Crystallographic and magnetic structures of Pr_6Fe_13Ge have been investigated by high-resolution powder neutron diffraction in the temperature range of 10－300 K. The magnetic structure consists of ferromagnetic Pr_6Fe_13 slabs that alternate antiferromagnetically, along c, with the next Pr_6Fe_13 slab separated by a non-magnetic Ge layer. The magnetic moments lie within the ab-planes. The propagation vector of this structure is k=(001) with respect to the conventional reciprocal lattice of the I-centred structure. However, the temperature-dependence of neutron-scattering intensity of the (110) Bragg peak, very similar to the temperature-dependent magnetization measured by SQUID magnetometer, indicates that a small c-axis ferromagnetic component should be added to the above antiferromagnetic model.