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High-Temperature Molecular Magnets Based on Cyanovanadate Building Blocks: Spontaneous Magnetization at 230 K
The molecular-based magnetic materials Cs$_2$Mn$^{II}$[V$^{II}$(CN)$_6$] (1) and (Et$_4$N)$_{0.5}$Mn$_{1.25}$-[V(CN)$_5$]$\cdot$2H$_2$O (2) (where Et is ethyl) were prepared by the addition of manganese(II) triflate to aqueous solutions of the hexacyanovanadate(II) ion at 0°C. Whereas 1 crystallizes...
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Published in: | Science (American Association for the Advancement of Science) 1995-04, Vol.268 (5209), p.397-400 |
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Main Authors: | , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | The molecular-based magnetic materials Cs$_2$Mn$^{II}$[V$^{II}$(CN)$_6$] (1) and (Et$_4$N)$_{0.5}$Mn$_{1.25}$-[V(CN)$_5$]$\cdot$2H$_2$O (2) (where Et is ethyl) were prepared by the addition of manganese(II) triflate to aqueous solutions of the hexacyanovanadate(II) ion at 0°C. Whereas 1 crystallizes in a face-centered cubic lattice, 2 crystallizes in a noncubic space group. The cesium salt (1) has features characteristic of a three-dimensional ferrimagnet with a Néel transition at 125 kelvin. The tetraethylammonium salt (2) also behaves as a three-dimensional ferrimagnet with a Néel temperature of 230 kelvin; only two other molecular magnets have higher magnetic ordering temperatures. Saturation magnetization measurements indicate that in both compounds the V$^{II}$ and high-spin Mn$^{II}$ centers are antiferromagnetically coupled. Both 1 and 2 exhibit hysteresis loops characteristic of soft magnets below their magnetic phase-transition temperatures. The high magnetic ordering temperatures of these cyano-bridged solids confirm that the incorporation of early transition elements into the lattice promotes stronger magnetic coupling by enhancing the backbonding into the cyanide π$^*$ orbitals. |
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ISSN: | 0036-8075 1095-9203 |
DOI: | 10.1126/science.268.5209.397 |