Chemical bonding inV(TCNE)x(x∼2)thin-film magnets grownin situ<

The unoccupied electronic structure of the semi-conducting room temperature molecular magnet V(TCNE)2

“…There is simple charge transfer between the sodium atom and the V(TCNE) x system and no evidence for covalent bonding between sodium and V(TCNE) x is present in the spectra. More thorough discussions of pristine V(TCNE) x has been published earlier [13,14], but a short summary of each core level and each absorption edge is also given here for the convenience of the reader.…”

“…Though the magnetic and electric (transport) response of V(TCNE) x has been characterized [8,11], the electronic structure of the material was until recently unknown [12][13][14]. This has greatly hampered the development of this class of magnets since knowledge about the frontier occupied and unoccupied molecular orbitals are of crucial importance to the electronic and magnetic properties.…”

“…As a result of the un-known physical structure of V(TCNE) x , theoretical calculations of the V(TCNE) x electronic structure have been impossible, but by using a model system of V(TCNE) x , namely alkali-doped TCNE, we have been able to partially circumvent this problem and theoretical results of alkali-doped TCNE have proven valuable in the interpretation of the experimental photoelectron spectroscopy (PES) and near edge x-ray absorption fine structure (NEXAFS) spectra of alkali-doped TCNE as well as of the more complex V(TCNE) x [12][13][14]. The first results on the occupied electronic structure were obtained from a study of the model compound Rb(TCNE) [12] and have been compared with results on V(TCNE) x films that were prepared by a recently developed in-situ CVD method, enabling for the first time preparation and characterization of oxygen-free V(TCNE) x films [13].…”

“…Development of chemical vapor deposition (CVD) fabrication techniques has however improved stability and reproducibility of the material [13][14][15][16][17]. An extended x-ray absorption fine structure (EXAFS) study has probed the local structure of the compound, showing that the vanadium ion coordinates to about six nitrogen atoms, most likely in a slightly distorted octahedral environment, each with an average distance in room temperature of 2.084(5) Å [18].…”

“…The studies showed that there are strong hybridization between the vanadium and the TCNE in the occupied electronic structure. The strong hybridization between the TCNE and vanadium ions in the occupied electronic structure has also been modeled using ligand field multiplet (LFM) calculations and charge transfer multiplet (CTM) calculations in combination with NEXAFS and x-ray magnetic circular dichroism (XMCD) experimental data yielding an estimate of a hybrid V(3d)-CN highest occupied molecular orbital (HOMO) given by 60% 3d 3 and 40% 3d 4 L, where L is a hole on the cyano ligands [14]. Hence, the frontier occupied electronic structure is more complex than the previous proposed model [11] and the nature of the unoccupied electronic structure is to date unknown.…”