A Site-Ordered Quadruple Perovskites, RMn<sub>3</sub>Ni<sub>2</sub>Mn<sub>2</sub>O<sub>12</sub> with R = Bi, Ce, and Ho, with Different Degrees of B Site Ordering
A site-ordered quadruple perovskites, AA′<sub>3</sub>B<sub>4</sub>O<sub>12</sub>, can have 3<i>d</i> transition metals at A′ and B sites, and show complex magnetic interactions and behavior. Additional complexity appears when B site-ordered arrangement...
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| Format: | Article |
| Language: | English |
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MDPI AG
2025-04-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/8/1749 |
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| Summary: | A site-ordered quadruple perovskites, AA′<sub>3</sub>B<sub>4</sub>O<sub>12</sub>, can have 3<i>d</i> transition metals at A′ and B sites, and show complex magnetic interactions and behavior. Additional complexity appears when B site-ordered arrangements are realized in AA′<sub>3</sub>B<sub>2</sub>B′<sub>2</sub>O<sub>12</sub>. In this work, A site-ordered quadruple perovskites, RMn<sub>3</sub>Ni<sub>2</sub>Mn<sub>2</sub>O<sub>12</sub> with R = Bi, Ce, and Ho, were prepared by a high-pressure, high-temperature method at about 6 GPa and about 1500 K. The R = Bi and Ce samples were found to crystallize in space group <i>Im</i>-3 with a disordered distribution of Ni<sup>2+</sup> and Mn<sup>4+</sup> cations in one B site. On the other hand, the R = Ho sample crystallized in space group <i>Pn</i>-3 and showed partial ordering of Ni<sup>2+</sup> and Mn<sup>4+</sup> cations between two B sites. The structural data (and bond valence sums) suggest that cerium has the oxidation state +3, which is unusual for such perovskites. Magnetic properties were investigated by magnetic susceptibility and specific heat measurements, which showed the presence of one magnetic transition near 36 K for R = Bi; there was evidence for the presence of two magnetic transitions near 27 K and 33 K for R = Ce, and near 10 K and 36 K for R = Ho. Curie–Weiss parameters were estimated for all samples from high-temperature magnetic measurements up to 750 K. The total effective magnetic moment for R = Ce also suggests the presence of Ce<sup>3+</sup>. A magnetic field of 90 kOe had the largest effect on the specific heat of the R = Ho sample, and almost no effects on the specific heat of the R = Bi sample. |
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| ISSN: | 1420-3049 |