Abstract
New exotic phenomena have recently been discovered in oxides of paramagnetic Ir4+ ions, widely known as ‘iridates'. Their remarkable properties originate from concerted effects of the crystal field, magnetic interactions and strong spin-orbit coupling, characteristic of 5d metal ions. Despite numerous experimental reports, the electronic structure of these materials is still challenging to elucidate, and not attainable in the isolated, but chemically inaccessible, [IrO6]8– species (the simplest molecular analogue of the elementary {IrO6}8− fragment present in all iridates). Here, we introduce an alternative approach to circumvent this problem by substituting the oxide ions in [IrO6]8− by isoelectronic fluorides to form the fluorido-iridate: [IrF6]2−. This molecular species has the same electronic ground state as the {IrO6}8− fragment, and thus emerges as an ideal model for iridates. These results may open perspectives for using fluorido-iridates as building-blocks for electronic and magnetic quantum materials synthesized by soft chemistry routes.
Highlights
Duisburg-Essen (CENIDE), Universitat Duisburg-Essen, 47048 Duisburg, Germany
Their local magnetic properties are probed by X-ray magnetic circular dichroism (XMCD) spectroscopy demonstrating that the [IrF6]2 À and {IrO6}8 À units possess virtually identical electronic ground states as suggested by theory[17]
The ultimate dimensional reduction to molecular {MOx}y À is impeded by the progressive development of large localized negative charges
Summary
Birol and Haule[17] recently suggested that the design of materials incorporating isolated IrIV octahedra should facilitate smaller bandwidths and promote Mott ground states If this strategy is developed to its logical end, a discouraging result is obtained as the isolation of the [IrO6]8 À ion (Fig. 1b) is chemically impossible. For the realization of dimensionally reduced oxido-iridates, the fluoride ion appears as an ideal substitute to oxide being isoelectronic with comparable chemical and physical characteristics, but, importantly, with a reduced charge Along this idea, we present the synthesis of molecular fluorido-iridates incorporating spatially isolated [IrF6]2 À units. We present the synthesis of molecular fluorido-iridates incorporating spatially isolated [IrF6]2 À units Their local magnetic properties are probed by X-ray magnetic circular dichroism (XMCD) spectroscopy demonstrating that the [IrF6]2 À and {IrO6}8 À units possess virtually identical electronic ground states as suggested by theory[17]. This fluorido-iridate moiety and its intrinsic properties, experimentally determined in this work, can be confidently used to model and emulate the basic {IrO6}8 À unit in oxido-iridates
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