Helimagnetic order in ferric arsenate, FeAsO₄

Abstract

High-resolution time of flight neutron powder diffractometry has been used to determine the antiferromagnetic structure of ferric arsenate at 4.2 K. The structure is incommensurate with a magnetic propagation vector (0.04994(3), 0, -0.24725(2)) in the a*-c* plane of the monoclinic unit cell. The spins of 4.01(2) µB on the Fe3+ ions rotate in a plane containing b* and making an angle of 34.1(7)° to [001] in β obtuse. The structure shows that the dominant antiferromagnetic coupling is between Fe3+ ions which are linked through tetrahedral arsenate groups giving a frustrated exchange network.

Structural chemistry and magnetic properties of Ln MnFeGe 4 O 12 ( Ln = Y, Eu, Lu)

“…The relatively low value of the ordered cation moment determined by neutron diffraction for LuMnFeGe 4 O 12 is consistent with this explanation. The values measured for the Y 3+ -and Eu 3+ -containing compositions lie within the range observed previously in comparable compounds [2,3]. Magnetic structures similar to that adopted by the three LnMnFeGe x Co x Ge 4 O 12 lead us to suggest that the occurrence of a doubled magnetic unit cell and the location of the ordered moment within the (001) plane might both be attributable to the presence of the single-ion anisotropy associated with Co 2+ but the magnetic structures determined in the current study show that this is not the case.…”

“…Over the years, magnetic superexchange interactions that involve multi-atom pathways, sometimes dubbed super-superexchange interactions, have been the focus of many studies, both experimental and computational, with arsenates, phosphates, sulfates and germanates being amongst the compounds investigated [1][2][3][4]. Our own recent research has centred on the family of germanates described by the general formula AM 2-x M' x Ge 4 O 12 , where M and M' are paramagnetic cations and A is a diamagnetic cation.…”

In situ and ex situ study of the enhanced modification with iron of clinoptilolite-rich zeolitic tuff for arsenic sorption from aqueous solutions

“…8). The signals at 2Θ values of 26.6 • and 27.4 • emerging in the samples immersed during three days, were similar to those observed as most intensive peaks in ferric arsenate FeAsO 4 [47]; while those at 28 • and 29.6 • (after one day), and 41.7 • (after three days) could not be assigned to any related species. Further we concentrated on the analysis of iron in the dry samples of this three days trial to test the proposition that oxidation of arsenite to arsenate in the solution should have led to the reduction of ferric iron to ferrous iron in the zeolite.…”

Multidataset refinement resonant diffraction, and magnetic structures

“…Low angle detectors on instruments utilising thermal neutron pulses can also be used, although the ∆ d / d resolution is generally lower. Time-of-flight data have been used to solve the incommensurate magnetic structure of monoclinic FeAsO 4 [ 21 ], and to obtain precise refinements of the spiral periodicity in β-CrPO 4 and vanadate-doped samples [ 22 ]. The latter study showed that the spiral magnetic structure of β-CrPO 4 is not triply commensurate with the lattice periodicity through a precise determination of the ( q x ,0,0) propagation vector.…”