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| Home > Publications database > Transition metal carbodiimides –A new playground for solid-statephysics? |
| Conference Presentation (Invited) | FZJ-2025-04084 |
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2025
Abstract: Transition metal oxides, particularly those with partially filled 3d shells, have been the playgroundfor solid-state physics for many decades. These correlated oxides exhibit a competition betweencoulombic repulsion, which tends to localize electrons, and hybridization, which promotes delocalization,that leads to numerous many-body effects such as metal-insulator transitions, colossalmagnetoresistance and superconductivity, to name but a few. Traditionally the modification of suchphases, to imbue different physical properties, has relied on the doping of one cation for another toadjust both the electron count and degree of correlation. However, an alternative strategy may alsobe employed via anion substitution. Enter the divalent carbodiimide anion, <sup>−</sup>N=C=N<sup>−</sup>,which is well considered a pseudo-oxide, but with enhanced covalent character [1]. Indeed, numerousquasi-binary transition metal carbodiimides, M<sub>x</sub>(NCN)<sub>y</sub>, have nowbeen prepared, including CuNCN which exhibits spin-liquid behavior and a resonating-valencebond ground-state [2]. Here, however, we will take a closer look at MnHf(NCN)<sub>3</sub> andFeHf(NCN)<sub>3</sub>, which are the first examples of transition metal carbodiimides with aperovskite-like AB(NCN)<sub>3</sub> composition [3]. These quasi-ternary phases adopt a chiralcrystal structure, with P6<sub>3</sub>22 symmetry, and magnetometry measurements on MnHf(NCN)<sub>3</sub>evidence strong AFM coupling of Mn<sup>2+</sup> centers, but no evidence for long-range order.This suggests a degree of magnetic frustration in MnHf(NCN)<sub>3</sub> and highlights that thetypes of quantum behavior observed in correlated oxides may also be accessible to their carbodiimideanalogs.
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