Superconducting materials borocarbides

The interesting feature is that the series of borocarbides represent all combinations of Tc and 7n and that both superconductivity and magnetism coexist at the highest ever reported temperature. This class of compounds led to further detailed studies to understand the interplay of superconductivity and magnetism, in addition to identifying new superconducting materials. 

Superconductivity has also been discovered in rather exotic materials, including the following Buckminsterfullerene (Cgo) doped with ICI Carbon nanotubes (superconductivity in just one direction) Nickel borocarbides, which contain Ni2 B2 layers alternating with R C sheets, where R is a rare earth element such as Er and organic superconductors that contain planar organic cations and oxoanions. Chemists and physicists continue to study these and other families of superconductors. 

After a short report on the discovery of the quaternary borocarbide superconductors in Section 1.1, for comparison a limited survey of other superconductors based on boron and/or carbon will be presented in Section 1.2 whereas the interplay of superconductivity and magnetism in other materials is discussed in Section 1.3. At the end of this section some special features of the RNi2B2C compounds and review articles in this field can be found in Section 1.4 as well as the further outline of this chapter. 

Technology as we have witnessed over the years has been outpacing any other development. Some of the developments in technology such as co-extrusion in copper, sintered material objects of required shapes, use of thin-film techniques to produce a tape for electrical connections and the fabrication of tapes and wires of superconductor Nb3Sn lend hope for future technological developments in superconducting rare earth materials such as borocarbides and YBaaCujOy. 

With the discovery of superconductivity (Tc = 15.5 K) in the Y-Ni-B-C system [6, 80], a new class of quaternary borocarbide superconductors has emerged. Superconductivity has been observed in several rare earth (Lu, Tm, Er and Ho) nickel borocarbides[80], and with transition metals such as Pd and Pt. The superconducting phase having the composition of YNi2B2C, crystallizes [81] in a tetragonal structure with alternating Y-C and Ni2B2 layers. Band structure calculations [82] indicate that these materials, unlike cuprate superconductors, are three-dimensional metals. 

S.-L. Drechsler, H. Rosner, S. V. Shulga, and H. Eschrig, Superconducting Transition Metal Borocarbides, in Proc. NATO Adv. Study Inst, on High-Tc Superconductors and Related Materials , ed. S.-L. Drechsler, T. Mishonov, Kluwer, Holland, 2001, p. 167. 

K-H. Muller, G.Drechsler, S-L. Fuchs, V. N. Narozh-nyi Magnetic, superconducting properties of rare earth borocarbides of the type RNI2B2C, Handbook of Magnetic Materials, Vol.14, ed. by K. H.J. Buschow (Elsevier, Amsterdam 2002) pp. 199-306 R. Flukiger, W. Klose (Eds.) Superconductors, Landolt-Bornstein, New Series 111/21 (Springer, Berlin, Heidelberg 1990)... 

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