Superconductivity in the Lanthanum-Yttrium-Manganese Alloy System

摘要

An empirical approach involving lattice instabilities was investigated in the search for new superconducting materials. Pseudo-lanthanide compounds using La and Y were prepared for the system La/sub 1-x/Y/sub x/Mn sub 2 by arc melting and subsequent heat treatment. Low temperature magnetic susceptibility and low temperature heat capacity measurements were made. The unit cell lattice parameters were determined from x-ray powder patterns taken on most samples and metallographic examination was carried out on selected samples. Alloys with low La concentrations (x greater than or equal to 0.6) showed RMn sub 2 in the cubic C15 Laves phase as the major component with second phase material present. The magnetic susceptibility and x-ray data indicated a superconducting phase which seemed to be the RMn sub 2 phase, but heat capacity measurements showed the second phase material was the superconductor, while the RMn sub 2 was not. Failure to form compounds with higher La content was experienced and may be due to the lattice instability expected at x = 0.56. This indicates that perhaps more stingent conditions are required to form pseudo-lanthanide compounds than were previously considered. More systems should be investigated to see if this is true, and to determine the possibilities of this approach. (ERA citation 05:017149)