New quaternary complex borides, Ti9M2Ru18B8 (Cr, Mn, Co, Ni, Cu, Zn): synthesis, crystal structure and bonding analysis

Fokwa, Boniface P. T.; Goerens, Christian; Gilleßen, Michael

doi:10.1524/zkri.2010.1239

Cited by 14 publications

(8 citation statements)

References 17 publications

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“…Another important factor for observing site preference is the occurrence of homoatomic distances similar to those found in the elemental crystal structures: The Cr–Cr distance found here, 2.642(9) Å, is not far from that found in one of the reported Cr modifications, 2.56 Å . Related observations occur in M x Rh 7– x B 3 and Ti 9– x M 2+ x Ru 18 B 8 , phases, in which the M (Cr–Ni) atoms also exhibit similar bond lengths, 2.59–2.63 Å in the former and 2.48–2.50 Å in the latter. However, an electronic contribution should not be neglected, as shown by density functional theory (DFT) calculations (see Electronic Structure and Chemical Bonding section below), which have also confirmed the site preferences found in this new structure.…”

Section: Results and Discussionsupporting

confidence: 75%

“…For example, the presence of well-separated linear chains of magnetically active M atoms, as in A 2 MT 5– x T′ x B 2 (A = Sc, Ti, Zr; T/T′ = Ru, Rh, Ir) compounds , c, and the recently discovered Nb 6 Fe 1– x Ir 6+ x B 8 , make them particularly attractive for studying anisotropic magnetic interactions. The presence of chains of Fe 2 dumbbells, that is, Fe ladders, in Ti 9 Fe 2 Ru 18 B 8 led to the first Ru-rich ferromagnetic boride . Furthermore, the above-mentioned chains and ladders were successfully combined in the compounds Ti 9– x M 2+ x Ru 18 B 8 (M = Fe, Mn) series en route to the first semihard ferrimagnetic transition metal borides in existence .…”

Section: Introductionmentioning

confidence: 99%

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Spin Frustration and Magnetic Ordering from One-Dimensional Stacking of Cr₃ Triangles in TiCrIr₂B₂

et al. 2016

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Spin-frustrated chains of Cr3 triangles are found in the new metal boride TiCrIr2B2 by synergistic experimental and theoretical investigations. Although magnetic ordering is found at 275 K, competing ferro- and anti-ferromagnetic interactions coupled with spin frustration induce a rather small total magnetic moment (0.05 μB at 5 T), and density functional theory (DFT) calculations propose a canted, nonlinear magnetic ground-state ordering in the new phase. TiCrIr2B2 crystallizes in the hexagonal Ti1+xOs2-xRuB2 structure type (space group P6̅2m, No. 189, Pearson symbol hP18). The structure contains trigonal planar B4 boron fragments with B-B distances of 1.76(3) Å alternating along the c-direction with Cr3 triangles with intra- and intertriangle Cr-Cr distances of 2.642(9) and 3.185(1) Å, respectively. Magnetization measurements of TiCrIr2B2 reveal ferrimagnetic behavior and a large, negative Weiss constant of -750 K. DFT calculations demonstrate a strong site preference of Cr for the triangle sites, as well as magnetic frustration due to indirect anti-ferromagnetic interactions within the Cr3 triangles.

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Section: Results and Discussionsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Spin Frustration and Magnetic Ordering from One-Dimensional Stacking of Cr₃ Triangles in TiCrIr₂B₂

et al. 2016

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“…The total DOS curves reveal a pseudogap at the corresponding Fermi levels, while invoking spin polarization results in the formation of large, localized magnetic moments at the Fe atoms and some polarization induced at the neighboring Ru atoms. An analysis of −COHP curves shows a bonding network similar to those described in Ti 9 Fe 2 Ru 18 B 8 and Ti 9 M 2 Ru 18 B 8 (M = Cr, Mn, Co, Ni, Cu, Zn). , Through an analysis of site energies and bond energies, Ti/Fe mixing may occur at both the 2b- and 4h-chain sites in Ti 9− n Fe 2+ n Ru 18 B 8 . Moreover, Fe substitution at the 4h-chain (M2) sites, which creates magnetic scaffolds, increases the local moments at the Fe1-‘ladder’ sites.…”

Section: Discussionmentioning

confidence: 62%

Scaffolding, Ladders, Chains, and Rare Ferrimagnetism in Intermetallic Borides: Electronic Structure Calculations and Magnetic Ordering

et al. 2011

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The electronic structures of "Ti 9-n Fe 2+n Ru 18 B 8 " (n = 0, 0.5, 1, 2, 3), in connection to the recently synthesized Ti 9-n Fe 2+n Ru 18 B 8 (n = 1, 2), have been investigated and analyzed using LSDA tight-binding calculations to elucidate the distribution of Fe and Ti, to determine the maximum Fe content, and to explore possible magnetic structures to interpret experimental magnetization results. Through a combination of calculations on specific models and using the rigid band approximation, which is validated by the DOS curves for "Ti 9-n Fe 2+n Ru 18 B 8 " (n = 0, 0.5, 1, 2, 3), mixing of Fe and Ti is anticipated at both the 2b-and 4h-chain sites. The model "Ti 8.5 Fe 2.5 Ru 18 B 8 " (n = 0.5) revealed that both Brewer-type Ti−Ru interactions as well as ligand field splitting of the Fe 3d orbitals regulated the observed valence electron counts between 220 and 228 electrons/formula unit. Finally, models of magnetic structures were created using "Ti 6 Fe 5 Ru 18 B 8 " (n = 3). A rigid band analysis of the LSDA DOS curves concluded preferred ferromagnetic ordering at low Fe content (n ≤ 0.75) and ferrimagnetic ordering at higher Fe content (n > 0.75). Ferrimagnetism arises from antiferromagnetic exchange coupling in the scaffold of Fe1-ladder and 4h-chain sites. Disciplines Materials Chemistry | Other Chemistry | Physical Chemistry CommentsReprinted (adapted) with permission from J. Am. Chem. Soc., 2011, 133 (17) In the past two decades a class of complex intermetallic borides has been synthesized containing magnetically active 3d atoms in close proximity to each other, allowing for studies of magnetic exchange as a function of valence electron count. 1À4 Some of these compounds are variants of the Zn 11 Rh 18 B 8 -type structure, which crystallizes in the P4/mbm (no. 127) space group. Substitution of zinc by both titanium and iron, along with replacing rhodium with ruthenium, leads to the previously reported compound Ti 9 Fe 2 Ru 18 B 8 . 5 This structure contains 'ladders' of iron atoms where the 'rungs' are formed by Fedimers with an interatomic distance of ca. 2.5 Å and separated by ca. 3.0 Å along the [001] direction. The distances are short enough for through-space magnetic exchange to occur; as a result, the magnetic properties of this compound were investigated both experimentally and theoretically. 5 Ti 9 Fe 2 Ru 18 B 8 was determined to order ferromagnetically with a magnetic moment of 1.2 μ B at 7 T and a Curie temperature (T C ) of 200 K. The Weiss constant (θ) is approximately þ290 K, further indicating a strong (FeÀFe) ferromagnetic exchange interaction. 5 The magnetic ordering was also predicted to be ferromagnetic by theory. An analysis of the crystal orbital Hamilton populations (ÀCOHP) and the density of states (DOS) curves showed the occupation of FeÀFe antibonding states and a local maximum in the nonmagnetic DOS at the Fermi level, both of which point toward electronic instability in the system. 6,7 Allowing the structure to relax through spin polarization resulted in the removal...

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“…When studying series 2 , we discovered Ti 9 Fe 2 Ru 18 B 8 (Zn 11 Rh 18 B 8 -type) in which Fe ladders were observed for the first time in intermetallic systems . We were then able to synthesize more than a dozen of similar compounds, Ti 9 M 2 Ru 18 B 8 (M = Cr, Mn, Co, Ni, Zn) and the substitutional variants Ti 9– x M 2+ x Ru 18 B 8 (M = Cr, Mn, Co, Ni; x = 0–2) . Experimental investigations confirmed Ti 9 Fe 2 Ru 18 B 8 as the first Ru-rich ferromagnet ( T C = 200 K), and theory identified spin-triplet Fe 2 dimers that are ferromagnetically coupled with neighboring Fe 2 dimers along the c -axis (Fe-ladder) to account for the unexpected magnetic behavior.…”

Section: Tuning Magnetic Properties By Modifying Crystal and Electron...mentioning

confidence: 87%

Boron: Enabling Exciting Metal-Rich Structures and Magnetic Properties

2017

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Boron's unique chemical properties and its reactions with metals have yielded the large class of metal borides with compositions ranging from the most boron-rich YB (used as monochromator for synchrotron radiation) up to the most metal-rich NdFeB (the best permanent magnet to date). The excellent magnetic properties of the latter compound originate from its unique crystal structure to which the presence of boron is essential. In general, knowing the crystal structure of any given extended solid is the prerequisite to understanding its physical properties and eventually predicting new synthetic targets with desirable properties. The ability of boron to form strong chemical bonds with itself and with metallic elements has enabled us to construct new structures with exciting properties. In recent years, we have discovered new boride structures containing some unprecedented boron fragments (trigonal planar B units, planar B rings) and low-dimensional substructures of magnetically active elements (ladders, scaffolds, chains of triangles). The new boride structures have led to new superconducting materials (e.g., NbRuB) and to new itinerant magnetic materials (e.g., NbFeIrB). The study of boride compounds containing chains (Fe-chains in antiferromagnetic ScFeRuB), ladders (Fe-ladders in ferromagnetic TiFeRhB), and chains of triangles (Cr chains in ferrimagnetic and frustrated TiCrIrB) of magnetically active elements allowed us to gain a deep understanding of the factors (using density functional theory calculations) that can affect magnetic ordering of such low-dimensional magnetic units. We discovered that the magnetic properties of phases containing these magnetic subunits can be drastically tuned by chemical substitution within the metallic nonmagnetic network. For example, the small hysteresis (measure of magnetic energy storage) of TiFeRhB can be successively increased up to 24-times by gradually substituting Ru for Rh, a result that was even surpassed (up to 54-times the initial value) for Ru/Ir substitutions. Also, the type of long-range magnetic interactions could be drastically tuned by appropriate substitutions in the metallic nonmagnetic network as demonstrated using both experimental and theoretical methods. It turned out that Ru-rich and valence electron poor metal borides adopting the TiCoB or the ThFe structure types have dominating antiferromagnetic interactions, while in Rh-rich (or Ir-rich) and valence electron rich phases ferromagnetic interactions prevail, as found, for example, in the ScFeRuRhB and FeRhRuB series. Fascinatingly, boron clusters (e.g., B rings) even directly interact in some cases with the magnetic subunits, an interaction which was found to favor the Fe-Fe magnetic exchange interactions in the ferromagnetic NbFeIrB. Using less expensive transition metals, we have recently predicted new itinerant magnets, the experimental proof of which is still pending. Furthermore, new structures have been discovered, all of which are being studied experimentally and computationally with the aim of...

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New quaternary complex borides, Ti₉M₂Ru₁₈B₈ (Cr, Mn, Co, Ni, Cu, Zn): synthesis, crystal structure and bonding analysis

Abstract: Powder samples and single crystals of the Ti

Cited by 14 publications

References 17 publications

Spin Frustration and Magnetic Ordering from One-Dimensional Stacking of Cr₃ Triangles in TiCrIr₂B₂

Spin Frustration and Magnetic Ordering from One-Dimensional Stacking of Cr₃ Triangles in TiCrIr₂B₂

Scaffolding, Ladders, Chains, and Rare Ferrimagnetism in Intermetallic Borides: Electronic Structure Calculations and Magnetic Ordering

Boron: Enabling Exciting Metal-Rich Structures and Magnetic Properties

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New quaternary complex borides, Ti9M2Ru18B8 (Cr, Mn, Co, Ni, Cu, Zn): synthesis, crystal structure and bonding analysis

Abstract: Powder samples and single crystals of the Ti

Cited by 14 publications

References 17 publications

Spin Frustration and Magnetic Ordering from One-Dimensional Stacking of Cr3 Triangles in TiCrIr2B2

Spin Frustration and Magnetic Ordering from One-Dimensional Stacking of Cr3 Triangles in TiCrIr2B2

Scaffolding, Ladders, Chains, and Rare Ferrimagnetism in Intermetallic Borides: Electronic Structure Calculations and Magnetic Ordering

Boron: Enabling Exciting Metal-Rich Structures and Magnetic Properties

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Product

Resources

About

New quaternary complex borides, Ti₉M₂Ru₁₈B₈ (Cr, Mn, Co, Ni, Cu, Zn): synthesis, crystal structure and bonding analysis

Spin Frustration and Magnetic Ordering from One-Dimensional Stacking of Cr₃ Triangles in TiCrIr₂B₂

Spin Frustration and Magnetic Ordering from One-Dimensional Stacking of Cr₃ Triangles in TiCrIr₂B₂