Incommensurate magnetic order in PrNiAl₄

The RNiAl₄ intermetallic series (where R = Ln³⁺) has been the subject of much investigation over a number of years. These compounds are known to possess some interesting magnetic behaviours including multiple magnetic phases and metamagnetism. TbNiAl₄, ErNiAl₄ and NdNiAl₄ are all known to have incommensurate magnetic structures determined from neutron diffraction, whereas the presence of an incommensurate magnetic phase in PrNiAl₄ is more tentative, based only on specific heat and magnetisation measurements. Recent neutron powder diffraction experiments have confirmed the presence of this incommensurate magnetic phase at 7 K and 7.5 K, well within the range of 6.9-8.1 K predicted by the specific heat data. Analysis of the diffraction patterns puts the propagation vector of the magnetic phase at k = (0.071(1), 1, 0), with the magnetic moments pointing along the a-axis. (author)