Investigation of the structure of the relaxor ferroelectric Pb(Fe_1/2Nb_1/2)O₃by neutron powder diffraction

Abstract

The complex perovskite lead iron niobate, Pb(Fe1/2 Nb1/2 )O3 (PFN), has been studied by neutron powder diffraction. Following collection of diffraction data at 300 K and at 10 K, structural refinements have been carried out by means of the Rietveld method. As expected, a straightforward unit cell of symmetry R 3m was obtained for the 300 K structure, with the same symmetry and a similar unit cell also obtained at low temperature. Furthermore, in order to obtain a good agreement with experiment at 10 K, it was necessary to assign non-zero magnetic moments to the iron ions, these being in a collinear, antiferromagnetic alignment. This magnetic structure can be described with reference to doubled unit cell axes. The factors governing the observed structures of PFN are discussed by comparison with the related system of Pb(Mg1/3 Nb2/3 )O3 .

Short- and medium-range structure of multiferroic Pb(Fe1/2Nb1/2)OJeong1, Ahn2, Kim3 et al. 2011Phys. Rev. B

“…Here we note that the thermal parameter of heavier Pb 2+ ion is a few times larger than that of lighter Fe 3+ /Nb 5+ ions at all temperatures. Similar results were reported in previous studies on PFN as well 21 . According to first-principles calculations on Pb-containing perovskite, Pb ions tend to avoid cube faces with high-valence ions and displace toward cube faces with low-valance ions 22 .…”

Low-temperature neutron diffraction and magnetic studies on the magnetoelectric multiferroic Pb(Fe0.534Nb0.4W0.066)O3

“…at B sites. This is similar to the behaviour of magnetic moments of Fe in other Pbbased systems [1,[37][38][39][40].…”

Composition dependent room temperature structure, electric and magnetic properties in magnetoelectric Pb(Fe 1/2 Nb 1/2 )O 3 Pb(Fe 2/3 W 1/3 )O 3 solid-solutions

“…Among these pure Raman active four modes are the A1g, Eg and 2F2g phonons, and the rest become visible in Raman spectra due to local structural distortions with respect to the ideal lattice. The approximate assignment of the modes in the From the refinement of ND data found that, Pb (Lead) is never in its ideal Wyckoff position [45,46] and also, the B site cations (Fe 3+ and Nb 5+ ) local ordering within a disordered matrix [47] and it is well supported by the Garcia -Flores et al [39] report. The presence of Fe 3+ cations in the octahedral B site, possible indirect magnetic nature of these modes can be considered since PFN presents, in addition to ferroelectric and magnetic properties, which is responsible for the peak at 791 cm −1 .…”