The electric field gradient at the iron sites inβFeOOH

Magnetic and crystal structure refinement in akaganeite nanoparticle

“…4.2 K Mo¨ssbauer spectrum can be adjusted by introducing three or four sextets. The derived hyperfine parameters for the three sextets model are very similar to the ones reported in the literature [2,8,9,13,14]. In the case of the four sextets model, we have found that there are different ways of fitting the spectrum.…”

“…Murad [2] proposed that the components arise because of the increasing distortion of mid-wall to channel near iron sites. Chambaere and De Grave [9] attributed the sites to two irons, one with O 3 (OH) 3 coordination and O 2 (OH) 4 coordination. Re´zel and Ge´nin [8] have suggested that replacement of Cl ions by OH ions in the structure is an important factor for the presence of different iron sites.…”

Size Distribution and Frustrated Antiferromagnetic Coupling Effects on the Magnetic Behavior of Ultrafine Akaganéite (β-FeOOH) Nanoparticles

“…14 However, some studies have pointed out that a more realistic description should consider shifts in the y-coordinate of the Cl sites and few additional vacancies randomly distributed. 14 These differences in the description of the crystallochemical properties of akaganeíte have provoked controversy in the interpretation of the Mossbauer spectra (summarized in the introduction of ref 16) because some of them considered the tetragonal unit cell in their interpretations 12,17 while others the monoclinic cell. 14,16 In addition, different locations of the chloride ions have been considered.…”

Microstructural changes in particles detected during the transformation from β-FeOOH to α-Fe2O3 in dense aqueous suspensions

“…On the basis of this fitting it is evident that two kinds of iron atoms contribute to the Mössbauer effect. The origin of these two doublets was in the past discussed by several research groups [15][16][17][18]. Recently, Barrero et al [19] have analyzed the Mössbauer spectra of ␤-FeOOH.…”