Solid , low-dimensional

In understanding the magnetic behaviour of solids it is necessary to take into 

The spin and lattice dimensionality of a system can best be determined by studying the thermodynamic behaviour of the system near the transition temperature. In the absence of these studies, one of the quantities of importance in determining the lattice 

Layered chalcogenides such as TaS2 can accommodate large molecules such as stearamide. We shall be discussing the intercalation chemistry of these and other layered materials in Chapter 8. TaS2 is metallic and superconducting [T = 0.8 K) and the superconducting transition is increased to 3.5 K by incorporation of pyridine the interlayer separation increases from 3 to 6 A. Octadecylamine increases the interlayer 

The polymer (SN) is not only metallic but becomes a superconductor at 0.26 K (Hatfield, 1978). Another quasi one-dimensional compound showing superconductiv- 

Since the early discovery of the large conductivity peak in TTF-TCNQ around 60 K (Coleman et al., 1973) (Fig. 6.47) many studies have been carried out on TTF-related systems (Subramanyam, 1981 Soos Klein, 1976). Some aspects related to conduction in these systems were mentioned in the previous section. (TMTSF)2C104 and related compounds (TMTSF = tetramethyltetraselenafulvalene) are found to show superconductivity at low temperatures (Jerome, 1985). 

Neutron scattering and HFEPR have been the two most important techniques for the investigation of low-dimensional magnetic solids. Pulsed magnetic fields and HFEPR frequencies of up to 1 THz have sometimes been required to obtain the full low-temperature magnetic phase diagram. Recent work is discussed below the review by Katsumata should be consulted for earlier work. 

The S = 1 AFM NDM AZ, Ni(C5Hi4N2)2N3(C104), which has a Haldane gap of about 20 K, has been studied at low field and above the field, at which the gap closes. A detailed frequency-field diagram was obtained along all three 

The material 3CuCl2.2dioxane consists of trimers of 5 = 1/2 spins, each with a spin of 3/2, weakly AFM coupled in ID. At low temperature it therefore approximates to an S = 3/2 AFM linear system. Measurements in fields up to 30 T, 780 GHz, showed the existence of three modes a mode (G) with an energy gap of 92 GHz, a paramagnetic branch (P) with g = 2.2 and no gap and a third ferrimagnetic mode (F) with high-field slope 2 r/3 at 1.6 K. The mode P was identified as the Zeeman transition between sublevels in S = 1/2 and 3/2 entities, the mode G as the direct excitation of the spin 1/2 entity and F the coupled mode of the stable S = 3/2 entity and the less stable S = 1/2 entity. The results differ from those observed for a real S = 3/2 chain due to the internal degrees of freedom of the 3/2 complex. 

The HFEPR of the 3D material Nd2BaNi05 has been studied as a preliminary experiment before investigating the transition to a ID Haldane system by forming mixed crystals with Y2BaNiOs. Measurements at 1.8 K were carried out at frequencies of up to 1.2 THz in a pulsed field of up to 30 T. The material is AFM with energy gaps of the two modes estimated to be 1 THz and 240 GHz. 

The compound Me2CHNH3CuCl3 consists of FM and AFM alternating Heisenberg chains with S = j. A pair of coupled spins with S = 1 should behave as a Haldane system and this was confirmed by magnetization measurements 

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Heeger AJ, McDiarmld AG (1980) Conducting Organic Polymers Doped Polyacetylene. In Alcacer L (ed) The Physics and Chemistry of Low-Dimensional Solids. Reidel, Dordrecht, p 353... 

Sheldrick WS, Wachhold M, Jobic S, Brec R, Canadell E (1997) New low-dimensional solids tellurium-rich alkali metal tellurides. Adv Mater 9 669-675 Zheng Zh, Greedan JE (2004) Rare earth elements and materials. In Meyers RA (ed) Encyclopedia of Physical Science and Technology - Inorganic Chemistry. Elsevier Science, URL ... 

Rouxel J (1992) Low-dimensional solids An interface between molecular and solid-state chemistry The example of chainlike niobium and tantalum chalcogenides. Acc Chem Res 25 328-336... 

March, N. Tosi, M. In Polymers. Liquid Crystals, and Low-Dimensional Solids, Chapter 8, Chandrasekhar, S., Ed. Plenum Press, New York, 1984. 

Potember RS, Poehler TO, Cowan DO, Bloch AN (1980) Electrical switching and memory phenomena in semiconducting organic charge-transfer complexes, hi Alcacer L (ed) The physics and chemistry of low dimensional solids. D. Reidel, Dordrecht... 

The remaining chapters each deal with a property or a special class of solid. Chapter 4 covers low-dimensional solids, the properties of which are not isotropic. Chapter 5 deals with zeolites, an interesting class of compounds used extensively in industry (as catalysts, for example), the properties of which strongly reflect their stracture. Chapter 6 deals with optical properties and Chapter 7 with magnetic properties of solids. Finally, Chapter 8 explores the exciting field of superconductors, particularly the relatively recently discovered high temperature superconductors. 

Many phenomena such as dislocations, electronic structures of polyacetylenes and other solids, Josephson junctions, spin dynamics and charge density waves in low-dimensional solids, fast ion conduction and phase transitions are being explained by invoking the concept of solitons. Solitons are exact analytical solutions of non-linear wave equations corresponding to bell-shaped or step-like changes in the variable (Ogurtani, 1983). They can move through a material with constant amplitude and velocity or remain stationary when two of them collide they are unmodified. The soliton concept has been employed in solid state chemistry to explain diverse phenomena. 

K2[Pt(CN)4]BrQ jxHjO (KCP) is an example of a one-dimensional compound (see Chapter 6 for a discussion of low-dimensional solids) consisting of parallel stacks of... 

There are many other low-dimensional solids that have not been included here, polydiacetylene (Bloor, 1985) being one of them. Porphyrinic molecular metals show anisotropic conductivity, where the charge carriers pertain to both the metal and the ligand (Hoffman Ibers, 1983). The conductivity reaches values greater than 10 ohm cm Mn some systems and does not appear to come down to the insulator value... 

Magnetic Properties of Low-Dimensional Solids. The Royal Society of London, pp. 115-24. 

Low-dimensional Solids. - 2.10.1 Introduction. The magnetic properties of one and two-dimensional arrays of localized spins coupled by Heisenberg exchange interactions have been studied as a rather specialized branch of theoretical physics since the earliest days of quantum mechanics. However, recent advances in theory, and the preparation of real materials that are a good approximation to the theoretical models, have made low-dimensional systems much more central to condensed-matter science. There is enormous scope for synthetic chemistry in this area and, as will be seen later in this section, many new materials have been discovered recently. 

What is so special about low-dimensional solids The key element here is the Mermin-Wagner theorem [2]. It states [3] that systems with short-range forces that are at finite temperature cannot undergo any phase transition to a state that breaks (1) a discrete symmetry in one dimension (d = 1) or (2) a continuous symmetry in one or two dimensions (d = 2). Why is this so ... 

Optical properties of organic conductors also reflect the appearance of the energy gap, 2A, in the electronic energy spectrum of low-dimensional solids. The approximate value for the total gap from the g-mode line shapes can be estimated by comparing the IR spectra of the organic conductor, measured for the frequencies above and below the energy gap sharp absorption bands are produced at the frequencies w < 2A, whereas for to > 2A sharp indentations occur [87,88]. 

J.-P. Farges, in Physics and Chemistry of Low-Dimensional Solids Proceedings of the NATO-ASI Conference, Tomar, Portugal, Aug. 26-Sept. 7, 1979 (L. Alcacer, ed.), D. Reidel, Dordrecht, The Netherlands, 1980, pp. 223-232. 

Fig. 4.115. Schematic representation of the discharge process in a (CH)x/LiCI04/Li rechargeable storage battery celt (A. J. Heeger and A. G. MacDiar-mid, in The Physics and Chemistry of Low Dimensional Solids, L Alcacer, ed., D. Reidel, Boston, 1980, P-45).

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