Correlation of chemical coordination and magnetic ordering inSr3YCo4O10.5+δ(

Denis Sheptyakov

¹

,

Vladimir Pomjakushin

²

,

Oleg A. Drozhzhin

³

et al.

Abstract

The crystal structure and magnetic ordering in Sr 3 YCo 4 O 10.5+␦ , ␦ = 0.02 and 0.26 compounds have been revisited in a detailed neutron diffraction study. The ordering is of G-type, with the magnetic Co moments being aligned along the c axis of the tetragonal cells. In contrast to the previous studies, we, however, find an important peculiarity of the magnetic structures in the title compounds, namely, the magnetic moment magnitudes are different in the layers containing Co ions with different oxygen coordination. Along with the modulation of the coordination type and charge state of Co ions along the c axis, the ordered magnetic moment magnitudes are varying concomitantly and thus the correlation between the charge and spin states of the Co ions has been directly observed.

Magnetic Ordering in Sr3YCo4O10+x

“…These images are from thin, single domain regions of the specimens (Supplementary Figure S1 containing lower magnification images show that the crushed powder SYCO specimens contain at least three, orthogonal domains). Figure 2 compares the experimental ABF-STEM image along a <100> p direction to a simulated image from the model proposed by Sheptyakov et al 3 (model A). Other proposed models (Nakao et al 4 (x = 0.5), Khalyavin et al 5 (x = 1), and Bettis et al 6 (x = 1), which we refer to as model B, C and D respectively) show practically identical simulated images (see Supplementary Figure S2).…”

“…There have been several contending structural models for SYCO, extracted from X-ray and neutron diffraction, but there is no consensus on the precise atomic structure of this material3456. The undisputed facts are that SYCO exhibits antiferromagnetic ordering with asymmetric spin-up and spin-down magnetic moments, characteristic of ferrimagnetism.…”

First-order magnetic phase transition in layered Sr3YCo4O10.5 + δ-type cobaltites

“…In [21], it was sug gested that a certain fraction of Co 3+ ions undergo the transition from the high spin to low spin state with a decrease in temperature. However, the neutron dif fraction studies do not reveal any anomalous decrease in the magnetic moment when the temperature is decreased [19,20,22]. In the whole temperature range below the magnetic ordering point, the antiferromag netic G type structure was observed, whereas it was impossible to reliably detect the ferromagnetic contri bution since it turned out to be quite small.…”

Coupled anion and cation ordering in Sr3RFe4O10.5 (R=Y, Ho, Dy) anion-deficientperovskites

“…An original aniondeficient perovskite structure was reported for cobaltites Sr 4À x R x Co 4 O 10.5 + d with R¼La, Y, Sm-Yb, 0.4rxr1.33, and -0.02rdr0.74 (the cation homogeneity range and the oxygen content vary depending on the R-type and might also depend on synthesis conditions, causing the discrepancy between published data) [27][28][29]. The idealized structure of these compounds with the Sr 4 RCo 4 O 10.5 composition corresponds to the layer sequence-CoO 2 -AO-CoO 5/4 & 3/4 -AO-CoO 2 - [30][31][32]. The anion vacancies are partially ordered in the (CoO 5/4 & 3/4 ) layers, giving rise to formally five-fold coordinated Co atoms.…”