9/15
COEXISTENCE OF MAGNETIC ORDER AND SUPERCONDUCTIVITY IN
RARE EARTH NICKEL BOROCARBIDES (RNi2B2C, R=Y, Lu-Gd)
Don Naugle
Texas A&M University
Superconductivity and magnetism are generally considered to be incompatible
states. There are several examples of materials, however, where these two
types of order can be observed simultaneously over a wide range of temperatures and
magnetic fields. The intermetallic RNi2B2C compounds exhibit rich behavior
(superconductivity with a relatively high transition temperature for rare earths Y and Lu,
coexistence of superconductivity for Tm, Er, Ho and Dy, and only magnetic order for Tb
and Gd while the compound with Yb is a heavy fermion metal with neither
superconductivity nor magnetic order above 50mK). Thus, dramatically different ground
states can be achieved in this family of metals with the same crystal structure and
similar valence electronic structure through simple replacement of the
rare earth element. The unusual properties of these borocarbides as
determined from transport measurements, including resistance, thermopower, thermal
conductivity and point contact tunneling spectroscopy, will be discussed.