Crystal-field excitations in high-Tcsuperconducting materials

Abstract

Abstract The discovery of high-Tc superconductivity in the perovskite-type copper-oxide compounds has given rise to a large amount of materials research. Of particular interest in determining the nature of the superconductivity is the effect of substituents at various sites in these compounds. It has been realized that the superconducting transition temperature is essentially unchanged upon replacing the Y and La ions by “magnetic” rare-earth (R) ions. This surprising observation is in contrast to conventional super-conductors, for which paramagnetic ions usually have a large detrimental effect on superconductivity. It is therefore important to achieve a detailed understanding of the low-energy electronic properties which define the magnetic ground state of the R ions. In particular, information on the crystalline-electric-field (CEF) interaction at the R site is highly desirable, for the following reasons: For many high-Tc compounds superconductivity and long-range three-dimensional magnetic ordering of ...