Structural and magnetic phases of Fe(ND3)(2)PO4

Abstract

Polycrystalline samples of Fe(ND3)2PO4 were prepared by means of a hydrothermal route and characterized using powder x-ray diffraction, scanning electron microscopy, chemical and thermal analysis, magnetic measurements, specific heat and neutron diffraction experiments. This material orders within an orthorhombic (Pnma space group) crystal structure at room temperature, but below 220 K the crystal structure changes towards a monoclinic P 21/n structure through a phase transition with almost no latent heat. Furthermore, the magnetic cell at 2 K is twice the size of the crystallographic cell observed at 80 K. The magnetic structure associated with the Fe(III) ions is thus commensurate with the crystal lattice having a propagation vector \vec k=(1/2, 0, 0) , the magnetic moments lying in the yz plane of the crystallographic cell.