Ferrimagnetic cagelikeFe4O6cluster: Structure determination from infrared dissociation spectroscopy

Abstract

Cationic iron-oxide clusters of several sizes and stoichiometries have been synthesized and studied isolated in the gas phase. Vibrational spectra of the clusters have been measured using resonant IR- With the continuous trend of increasing the density of electronic devices, novel concepts are needed to answer the increasing technical problems. Many of these concepts require the creation of dedicated nanosized building blocks with well understood and a priori designed properties. For application in quantum computing and storage, for example, chemically synthesized magnetic molecules were suggested as possible units. 1 In such a "bottom-up" approach, magnetic clusters represent the smallest chunks of matter where condensed matter properties start to appear, magnetic order, in particular. However, these properties are still drastically different from those of the bulk matter, making the clusters a new object of physical research. Such atomic clusters may be as small as containing only tens of atoms. 2 They allow a large freedom in manipulation through varying their composition and size, adding one atom at a time. 3 From various materials, transition-metal oxides represent the widest variety of phenomena, from ferroelectricity and magnetism to superconductivity, often combined. In cluster form, many unusual phenomena have been predicted. [4][5][6][7][8] The knowledge of their detailed magnetic, electronic, and ionic structure is essential for various applications, such as the formation of novel materials or design of next generation devices, to fundamental issues as the functioning of quantum and thermodynamics laws in ͑sub-͒ nanoscale systems.To explore the intrinsic properties of nanoparticles free of external perturbations, experiments are best performed in the gas phase. However, the experimental data on the properties of gas-phase transition-metal oxide clusters are still scarce. A preferred method to obtain information on structure and bonding is vibrational spectroscopy. Unfortunately, in most cases, isolated clusters can only be studied in molecular beams or ion traps 9 and the low particle density rules out direct absorption measurements. Furthermore, clusters are often produced in broad size distributions, making size selectivity essential. To overcome such problems, mass selected clusters can be embedded and accumulated in rare gas matrices. 10,11 In those experiments, interactions with the rare gas matrix may induce shifts of the absorption lines, and additionally, it cannot be excluded that structural changes during the deposition occur. Intense tunable infrared sources such as free-electron lasers allow different approaches. Thus, titanium 12 and zirconium 13 oxides were investigated with the help of infrared resonance enhanced multiple-photon ionization spectroscopy. Infrared photodissociation spectroscopy helped to determine the structure of oxide clusters of vanadium, 14 niobium and tantalum 15,16 as well as binary vanadium-titanium oxide clusters. 17 However, the possible existence of magnetic ord...

Geometric, electronic, and magnetic structure ofFexOy+clusters

“…Therefore, comparison with an experimental method to confirm the theoretical findings is essential. In this work, we combine previously reported experimental vibration spectra 30 …”

“…Especially for the B3LYP functional it has been shown that this results in good agreement between the geometric structure and vibrational spectra for clusters. 28,30,37 However, hybrid functionals are quite computationally expensive compared to LDA and GGA functionals. Therefore, in the genetic algorithm we employ the GGA+U method to take into account that FeO clusters are strongly interacting systems.…”

Stable Stoichiometry of Gas-Phase Manganese Oxide Cluster Ions Revealed by Temperature-Programmed Desorption

“…This highly-symmetric structure is also common to other transition metal oxides such as Fe4O6 + , Sc4O6 + , and Nb4O10 + . [39][40][41] The bond dissociation energy of O2 from Mn4O6 + was calculated from the energy difference between Mn4O6 + and Mn4O4 + to be 1.8 eV. As Mn4O4 + was reported to have the ring structure, where Mn and O atoms were alternatingly-bridged, rupturing the bonds of bridging oxygen from Mn4O6 + was considered to require higher energy.…”

Structural, Vibrational, and Magnetic Properties of FeCoOn0/+ (n = 1–6) Bimetallic Oxide Clusters

“…However, several spectroscopic techniques have been developed which, in combination with density functional theoretic calculations, allow us to obtain the plausible geometric arrangement of the cluster. Examples are photoelectron spectroscopyi (PES), 16−19 infrared multiple photon dissociation spectroscopy (IR-MPD), 3,20,21 ion mobility spectrometry (IMS), 22,23 reactivity with CO, 24,25 and collisioninduced dissociation. 26−28 Recently, the fragmentation patterns of cobalt oxide clusters observed in mass spectrometry of jets of clusters produced by laser ablation 29,30 were rationalized by Aguilera-del Toro et al by means of density functional theoretic calculations.…”

“…Kirilyuk et al carried out IR-MPD experiments for cationic Fe oxide clusters of several sizes and stoichometries. 21 Comparing with density functional theory (DFT) calculations of the vibrational spectrum allowed them to determine the putative spin magnetic configuration of certain clusters. Ota et al studied Co oxide clusters by means of IMS.…”