Synthesis and structural characterization of the Ca2MnReO6 double perovskite

Abstract

The Ca2Mn1Re1O6 double perovskite has been prepared in polycrystalline form by using the encapsulated quartz tube method. The partial oxygen pressure inside the quartz tube revealed this to be a crucial synthesis parameter for the production of a single structural phase sample. This parameter was controlled using the ratio between ReO2 and ReO3 content and the filling factor parameter (ratio between mass and total inner volume of the quartz tube). The morphology and chemical composition was investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy. The crystal structure parameters were determined by analysis of the synchrotron high-resolution X-ray powder diffraction pattern. The analysis indicates that the sample is an ideal single-phase compound with a monoclinic crystal structure (space group P2(1)/n) with a = 5.44445(2) Å; b = 5.63957(3) Å; c = 7.77524(3) Å; and β = 90.18(1)º. Computer simulations were performed considering two cation valence configurations, namely, (i) Mn2+Re6+ or (ii) Mn3+Re5+, for the Ca2Mn1Re1O6 compound. XANES analysis measurements indicated +2.3 for the average valence of Mn (a mixture of Mn2+ and Mn3+) and +5.7 for the effective valence of Re (an intermediate valence between Re4+ (ReO2) and Re6+ (ReO3)). As a summary, we concluded there is a mixed valence configuration for Mn and Re in Ca2Mn1Re1O6 , taken into account the oxygen content of 6.0±0.1.

The Effect of Replacement of Zn <sup>2+</sup> Cation with Ni <sup>2+</sup> Cation on the Structural Properties of Ba sub>2</sub>Zn sub>1–x </sub>Ni sub>x</sub>WO sub>6</sub> Double Perovskite Oxides (X = 0, 0.25, 0.50, 0.75, 1)

“…The tolerance factor is calculated and is found to be between (1.008 -1.020) as shown in Table 1. This is confirmed the (Fm-3m) cubic structure according to the criteria adopted by Correa et al and Popov et al [12] [13]. Figure 4(a) and Figure 4(b) show the relation between the tolerance factor and volume of unit cell respectively with ratio of replacement.…”

Structural and magnetic investigation of Ca2MnReO6 doped with Ce

“…A major consequence of the distortion is that the Mn-O-Re angle is considerably lower than 180º. The relevant bond-lengths and angles are shown in Table II. No secondary phases or impurities were observed in the diffraction pattern of Ca 2 MnReO 6 and the structural parameters are the same to the ones reported by Corrêa et al [16] and similar to the ones reported by Kato et al [22]. Residual traces of CeO 2 were found in the Ca 1.8 Ce 0.2 MnReO 6 , which was remarked as second set of tick marks in the diffraction pattern (Fig.1b).…”

“…However, we used the notion of first moment (E m ) of the white-line proposed by Alp et al [26] to estimate the chemical shift. This notion also was used by Popov et al [6] and Corrêa et al [16]. The values found were ~ +5.7 and ~ +5.8 to Ca 2 MnReO 6 and Ca 1.921 Ce 0.079 MnReO 6 samples, respectively.…”

“…NIST standard reference material Al 2 O 3 was measured in the same experimental conditions in order to obtain the instrumental parameters. The GSAS program [14] with the EXPGUI interface [15] was used for the Rietveld analysis and the structure reported by Corrêa et al [16] was used as the input for the refinement.…”

Complex Ferrimagnetism and Magnetoresistance Switching in Ca-Based Double Double and Triple Double Perovskites

“…Hence Cu-substitution into CMFR to give CMCFR promotes metallicity and leads to an increase in both ordering temperatures and saturated magnetisation. Fe 3+ and Re 5+ are present at the B-sites in the above materials, but the double perovskites Ca2MnReO6 21 and Mn2MnReO6 12 are found to have Mn 2+ and Re 6+ , so the composition CaMnMnReO6 (CMMR) has been investigated to discover if the same charge configuration can be stabilized in the P42/n double double perovskite arrangement. This phase was successfully synthesized with a small 3.6(2) % impurity of MnO and structure refinement against PND data reveals a high degree of cation order with 4.0(1)% of Mn/Re antisite disorder, and also 5.4(2)% Mn occupancy of the Ca site.…”