Structure and magnetism of new hybrid cobalt hydroxide materials built from decorated brucite layers

Abstract

IntroductionThe properties of all functional electronic materials are determined by their composition and their structure. It is an ultimate goal for materials scientists to form new materials with such precise structural control as to give completely predictable electronic properties. Fortunately this ambition remains largely beyond our grasp, allowing synthetic chemists the frequent pleasure of surprise in what they may make.However, there are many important structural features which are amenable to some level of control such as the characteristic dimension of a material which has implications for many physical properties. One way to control dimensionallity is to build materials from components with different characters, typically in which the nature of electron-electron interactions varies greatly, and in which it is possible to physically segregate these parts on a microscopic level. Such a spatial confinement can be achieved in composite or hybrid materials in which characteristic "organic" ii) The M II can be replaced by a M III ion, which is coupled to the incorporation of a Fig. 1 a); 1 / 7 the maple leaf net (Fig. 1b), and so on. The first members of this series of trigonally symmetric networks are shown in ESI Figure S1. Although trigonal symmetry can be important for 2-D spin frustration, it is not a guarantee of a non-bipartite lattice. phase. Adjusting the synthetic conditions proved more fruitful and the yield of 3 was increased from a few crystals to an extractable and manageable quantity (~10 mg).We believe that there may be a correlation between the "ease of synthesis" and the role of the Na + and K + cation in the respective structures. Crystal StructuresThe structures were determined by single crystal X-ray diffraction. See Table 1 and Experimental Section for measurement, solution and refinement details. Structure of 1.The compound Co 12 (OH) 18 (ox) 3 (pip) (1) crystallises in the trigonal space group 3 P (# 147) and consists of two types of alternating layers ( Structure of 2 and 3.Compounds 2 and 3 are essentially isomorphous and isostructural crystallising in the polar trigonal space group P31c (# 159). The difference between the compounds is the alkali metal cation (Na in 2, K in 3), differences in crystal quality result in small differences between refined models (see Experimental Section). We describe the structure of 2 and give comparable details for 3 in square brackets. (Fig. 3).As with 1, the cobalt/hydroxide layer (type 1) is based on the brucite structure, although here we see a periodic loss of three out of every nineteen cobalt ions from the octahedral sites within the layer, giving the network structure shown in Figure 1d.These layer defects occur in groups of three centred about the three-fold crystallographic axis at ( 1 / 3 , 1 / 3 , c). The remaining octahedral cage of oxygen atoms forms the basal set for two tetrahedrally coordinated cobalt ions, which decorate the layer (Fig. 3b). The apical hydroxide of the CoO 4 tetrahedra is µ 3 -bridging two further Co 2+ ions wit...

Spin-half Heisenberg antiferromagnet on two archimedian lattices: From the bounce lattice to the maple-leaf lattice and beyond

“…This antiferromagnetic system is geometrically frustrated and it is related to several magnetic materials which have been experimentally investigated recently. 40,41,43 On the classical level the ground state is a commensurate non-collinear antiferromagnetic state. To study the quantum GS of the spin-half model we use the CCM for infinite lattices and the ED for finite lattices of N = 18 and N = 36 sites.…”

“…It is interesting to point out that the discussion of the magnetic properties of the HAF on Archimedian lattices is not only a challenging theoretical problem of quantum many-body physics but that it is also strongly relevant to experiment. Indeed, most of these lattices are found to be underlying lattice structures of the magnetic ions of various magnetic compounds, such as CaV 4 O 9 37 , SrCu 2 (BO 3 ) 2 38 , or [Fe 39 Recently there has been also synthesized the magnetic compound 40) with maple-leaf lattice structure as well as hybrid cobalt hydroxide materials 41 with maple-leaf like lattice structure which may stimulate increasing interest in this lattice. Moreover, in the natural mineral spangolite (Cu 6 Al(SO 4 )(OH) 12 Cl•3H 2 0) the magnetic copper ions sit on the lattice sites of the maple-leaf lattice.…”

“…Indeed, most of these lattices are found to be underlying lattice structures of the magnetic ions of various magnetic compounds, such as CaV 39 Recently there has been also synthesized the magnetic compound 40) with maple-leaf lattice structure as well as hybrid cobalt hydroxide materials 41 with maple-leaf like lattice structure which may stimulate increasing interest in this lattice. Moreover, in the natural mineral spangolite (Cu 6 Al(SO 4 )(OH) 12 Cl·3H 2 0) the magnetic copper ions sit on the lattice sites of the maple-leaf lattice.…”

Antiferromagnetic Ising model on the sorrel net: a new frustrated corner-shared triangle lattice

“…It is our hope that our identification of this structure as an interesting frustrated lattice will encourage experimental groups to investigate materials naturally forming in this pattern, as has been the case with recent experimental searches for the maple leaf and kagome lattices. Indeed, one recent study 1 has managed to achieve a 1 9 th depleted triangular lattice in a magnetic system, although, as we discuss below in Sec. VI, the antiferromagnetic order seen may have resulted from additional hexagonal layers in this complex material.…”

“…Once again, the antiferromagnetic Ising model features a large residual entropy per spin, S N = 1 9 ln(72) ≈ 0.475185. 23 The maple leaf net 24 is a 1 7 th depleted triangular net, removing a triangular lattice formed by advancing along one basis vector by two units and a second by one unit in a manner similar to a knight in chess. The Ising model on this edge-sharing net, which has coordination number 5 in contrast to the triangular (6) and triangular kagome and kagome (4) coordinations, appears to have not yet been studied.…”