Magnetic ordering of PrCoAl4 a neutron diffraction study

Abstract The magnetic ordering of the orthorhombic (Pmma space group) PrCoAl 4 compound has been studied by neutron diffraction. Only the Pr moments order. Below T N =17 K they adopt a longitudinal amplitude modulated structure. The magnetic moments are confined to the c direction with the wave vector q =(0,0, q z ) with an almost temperature independent length. At 1.5 K the amplitude of the wave is 2.24(4) μ B /Pr atom and the wave vector q z =0.437(2) can be approximated within error limits by a rational fraction 11 25 which alternatively gives the possibility to consider the structure as a commensurate phase.