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  Reehuis, M.; Kotzyba, G.; Jeitschko, W.; Hofmann, M.: Commensurate ferrimagnetic and incommensurate antiferromagnetic order in the ThCr₂Si₂-type phosphide PrFe₂P₂. Journal of Magnetism and Magnetic Materials 221 (2000), p. 307-316

10.1016/S0304-8853(00)00505-9

Abstract:
The nuclear and the magnetic structures of PrFe2P2 have been investigated by neutron powder diffraction. Complementary studies of the magnetic order were carried out on single crystals of PrFe2P2 using a SQUID magnetometer. The nuclear structure of this phosphide was confirmed to be isotypic with ThCr2Si2 (space group I4/mmm, Z = 2). No magnetic order could be found for the iron atoms down to 1.6 K. The order of the praseodymium moments is antiferromagnetic with a most likely incommensurate sine-wave modulated magnetic structure from the Neel temperature T(N) = 28(1)K down to 16 K. The propagation vector is k = (0, 0, 0.799(3) and the moment direction is parallel to the tetragonal c-axis. Below 16 K the magnetic structure changes to a corresponding square-wave modulated structure. The presence of a net ferromagnetic component mu (exp) = 0 600(6) mu(B) along the c-axis indicates a commensurate ferrimagnetic structure with k = (0, 0, 4/5) and a magnetic unit cell of a x b x 5c, where the Pr moments have the spin sequence + - + + - + - + + -, + - ... along the tetragonal axis. The magnetic moment mu (exp) = 3.00(3)mu(B), is close to the theoretical moment of the free Pr3+ ion mu (eff) = 3.20 mu (B). From the SQUID data a second-order crystal field parameter of B2,0) = - 5.8( +/- 0.2) K was deduced. (C) 2000 Elsevier Science B.V. All rights reserved.