: Extent of charge ordering by Mössbauer spectroscopy and high-intensity high-resolution powder diffraction

Recent Developments in the Methods and Applications of the Bond Valence Model

“…At higher temperatures all the Fe ions have bond lengths corresponding to the same nonintegral oxidation state, but below a transition, known as the Verwey transition, the different oxidation states tend to freeze out on particular sites. Karen et al examined the charge ordering in the perovskite-related compound EuBaFe 2 O 5 as a function of temperature using high resolution powder X-ray diffraction and Mössbauer spectroscopy. The structure determination showed that above 256 K all the Fe ions had bond valence sums of 2.5 vu.…”

Orbital occupancy evolution across spin- and charge-ordering transitions in YBaFe 2 O 5

“…12), typical also for other rare-earth variants of YBaFe 2 O 5 [13,[24][25][26], where the large dipolar field of the minority-spin electron in d xz nearly cancels the Fermi-contact field. This same electron makes the EFG large (Fig.…”

“…Since V zz of charge-ordered Fe 2+ is along b and the magnetic moments too [13,[24][25][26], their angle β = 0°, and η (Eq. (1)) is needed to evaluate eQV yy so that Eqs.…”

Synthesis and magnetic properties of the double layer perovskite CeBaFe2O5+w

“…However, it seems that only trivalent states of the rare earth ions ͑R 3+ ͒ have been observed in RBaFe 2 O 5+w compounds that exhibit the Verwey transition. 3,9,15 In order to clarify the occurrence and effects of possible phase separation in this system, particularly in the CeBaFe 2 O 5+w compound, more work is still underway.…”

“…However, this structure is expected to be stable only at low temperatures, 9 or when just Fe 3+ ions are present in the CeBaFe 2 O 5+w sample, which implies w = 0.5 by assuming the presence of only Ce 3+ and Ba 2+ ions. However, in this ordered structure no Verwey transition is expected to occur, according to the model of electron hopping between Fe 2+ and Fe 3+ ions.…”