Enhancing spin state phase separation by strontium addition in the Y (Ba_1−xSr_x)Co₂O_5.5layered cobaltite

Abstract

In this paper we present a neutron diffraction study of the effects of replacing Ba with smaller Sr cations in the layered cobaltite YBaCo(2)O(5+δ) for δ≈0.5. Neutron thermodiffractograms are reported in the temperature range 20 K≤T≤300 K, as well as high-resolution neutron diffraction experiments at selected temperatures. The systematic refinement of the series of samples with Sr substituting at the Ba site permits the understanding of the complex magnetic behaviour of this system, and reinforces a two-phase scenario for the parent compound. We have found that Sr addition destabilizes the ferrimagnetic spin state ordered phase, as well as the '122' order characteristic of cobaltites with δ = 0.5, favouring instead a tetragonal and less ordered structure.

The ferromagnetic and antiferromagnetic phases in anion deficient La0.5−xPrxBa0.5CoO3−δ cobaltites

“…It is worth emphasizing that phase segregation into electronrich (ferromagnetic) and electron-poor (antiferromagnetic) phases was earlier claimed for layered cobaltites LnBaCo 2 O 6Àd (Ln-lanthanide). 35 The NPD data permit to clarify the magnetic structure of the La 0.5 Ba 0.5 CoO 2.88 . Taking into account the SPD data for La 0.5 Ba 0.5 CoO 2.88 , the additional peaks occurring only on NPD patterns below 150 K can be referred to magnetic neutron scattering (Fig.…”

High-temperature behavior of Sr-doped layered cobaltites Y (Ba1 −xSrx)Co2O5.5: phase stability and structural properties

“…The polycrystalline samples used in the present work correspond to those reported in Refs. [13] for x Sr = 0 and [14] for x Sr = 0.05 and x Sr = 0.10. Between the previous and present experiments, samples were stored in a dessicator containing silica gel, at room temperature (RT) and ambient pressure.…”

Studies in materials science and magnetism at Centro Atómico Bariloche using neutron powder diffraction

“…The study on samples substituted with Sr at the Basite confi rmed the phase-separation scenario [19,20]. We found that Sr addition destabilizes the ferrimagnetic SSO phase, as well as the "122" order, favoring instead a tetragonal and less ordered structure (Figure 3).…”

“…Moreover, the member with R = Ca was recently found to be multiferroic [22]. Data were collected at ILL (D20) with λ ∼ 2.42 Å in the temperature range 20-310 K (adapted from [19]). It is only through NPD experiments that the identity of these arrangements could be revealed (Figure 4), giving us a clue on the relevant magnetic interactions in the system, and unveiling how their stability may be tuned using variables such as composition, magnetic fi eld and temperature.…”