Developments in Ceramic Materials Research

Synthesis, Spectroscopic and Magnetic Studies… 129
The magnetic structure of the Cr2(P6O18) phase is shown in Figure 25 where only the
(CrO6) octahedron and magnetic moments are represented for clarity. The model implies
antiferromagnetic arrangements between the magnetic moments stabilising and overall threedimensional
(3D) antiferromagnetic order. The refined moments are aligned in the (100)
plane pointing 45.3° from the z axis (seee Figure 25). This value induces the weak
ferromagnetism detected in the magnetic measurements at low applied fields.
7.2. M(PO3)3 (M= Mo, Fe) Metaphosphates
The neutron diffraction patterns at 2 K for M(PO3)3 (M= Mo, Fe) were collected in the
D2B powder diffractometer and are represented in Figure 26. The patterns exhibit extra
magnetic peaks indicating than both compounds are magnetically ordered at 2 K. The
magnetic reflections for the molybdenum metaphosphate exhibit small intensities due to the
low ordering magnetic temperature observed in this compound. The thermal evolution of the
neutron diffraction patterns for Fe(PO3)3 was followed in the D1B instrument from 1.5 to 20
K.
M=Fe
M=Mo
2K
* *
RT
*
* 2K *
RT
Figure 26. Comparison of D2B neutron diagrams of (a) Mo(PO 3) 3 (λ= 1.594 Å) and (b) Fe(PO 3) 3 (λ =
2.41 Å), at room temperature and 2 K. The diagrams are shown as a function of the inverse of the d
spacing due to the different wavelengths used in the measurements. Magnetic ontribution an also
marked.