O Fischer – författare

It is matter of some surprise that this treasury of information concerning the centres of gravity of various parts of the human body has remained hidden not only from the English speaking world for obvious reasons, but also to some degree from the Ger­ mans themselves. What is less surprising is t!1at this work is a monument to the renouned German thoroughness as demon­ strated by the relentless pursuit of data and the meticulous ac­ curacy of the conclusions. However, these scientific investigations carried out in Leipzig must be viewed in the intellectual climate of the time. In the lat­ ter half of the nineteenth century, and later, Germany underwent an intellectual explosion. It was the age of Rhumkorff, Max Planck, the Weber brothers and Gottingen University. It was said that science came to life during discussions on the train be­ tween Gottingen and Berlin. So the scene was set and Braune and Fischer made good use of it and fulfilled their role as mem­ bers of the Royal Scientific Society of Saxony. When Pauwels (1935) analysed the static and dynamic forces exerted on the hip joint when standing and when walking, he needed data concerning the centres of gravity of the human body and of its different segments. I was faced with the same pre­ requisite when I studied the forces acting on the knee (1976).

The structural. electronic and lattice properties of superconducting ternary com­ pounds are the subject of this Topics volume. Its companion volume (Topics in Cur­ rent Physics. Volume 34) deals primarily with the mutual interaction of supercon­ ductivity and magnetism in ternary compounds. These two volumes are the culmination of a project. started nearly two years ago. that was inspired by the intense re­ search effort. both experimental and theoretical. then being expended to explore and develop an understanding of the remarkable physical properties of ternary super­ conductors. Research activity on this subject has increased in the meantime. The interest in ternary superconductors originated in 1972. when B.T. Matthias and his co-workers first discovered superconductivity in several ternary molybdenum sulfide compounds that had been synthesized in 1971 by R. Chevrel. M. Sergent. and J. Prigent. The superconducting critical temperature Tc of one of the compounds. PbMo S • was reported to be ~ 15 K. This value is sufficiently high that there was g 6 (and still is) reason to expect that other ternary compounds would be found with superconducting transition temperatures rivaling those of the A15 compounds. of which Nb Ge has the record high Tc of 23 K. The interest in ternary superconductors 3 received further impetus when several of the ternary molybdenum sulfides were found to have exceptionally high upper critical magnetic fields. some of them in the neighborhood of 50 Tesla or more. An immense amount of research on ternary molybdenum chalcogenides then followed.

This Topics in Current Physics (TCP) Volume 34 is concerned primarily with super- conductivity and magnetism, and the mutual interaction of these two phenomena in ternary rare earth compounds. It is the companion of TCP Volume 32 - Superconduc- tivity in Ternary Compounds: Structural, Electronic and Lattice Properties. The interplay between superconductivity and magnetism has intrigued theoreticians and experimentalists alike for more than two decades. V. L. Ginzburg first addressed the question of whether or not superconductivity and ferromagnetism could coexist in 1957, and B. T. Matthias and coworkers carried out the first experimental inves- tigations on this problem in 1959. The early experiments were made on systems that consisted of a superconducting element or compound into which small concentrations of rare earth impurities with partially-filled 4f electron shells had been intro- duced. These dilute impurity systems were chosen because the scattering of conduc- tion electrons by parama9. netic rare earth impurity ions usually has a strong de- structive "pa i r breaking" effect on superconducti vity, typi ca lly drivi ng the super- conducting transition temperature to zero at impurity concentrations of only a few atomic percent.Unfortunately, analysis of these early experiments was complicated by clustering and/or the formation of short range or "glassy" types of magnetic order so that definitive conclusions regarding the coexistence of superconductivity and magnetism could not be reached.