Three decades of prospecting for novel electronic states and phenomena in f-electron materials

Abstract

During the past three decades, f-electron materials have proven to be a rich reservoir of novel electronic states and extraordinary superconducting and magnetic phenomena, many of which are surveyed in this paper. The electronic states described include the non-magnetic Kondo many-body singlet, valence fluctuation, heavy fermion, and non-Fermi liquid states. The superconducting and magnetic phenomena recounted include reentrant superconductivity due to the Kondo effect or the onset of ferromagnetic order, the sinusoidally modulated magnetic state that coexists with superconductivity in ferromagnetic superconductors, coexistence of superconductivity and antiferromagnetic order, pressure-induced demagnetization of rare earth ions in dilute and concentrated rare earth systems, and anisotropic superconductivity in which the energy gap vanishes at points or on lines on the Fermi surface, possibly mediated by spin fluctuations, in heavy fermion f-electron and high- T c cuprate superconductors. The temperature vs. pressure or composition phase diagrams of f-electron compounds and high- T c cuprate superconductors in the vicinity of their antiferromagnetic quantum critical points are briefly compared.