From antiferromagnetic insulator to ferromagnetic metal: a brief review of the layered ruthenates

This paper presents a brief review of recent experimental results of the layered ruthenates (Sr, Ca)n+1,RunO3n+1, with n=1, 2, 3 and ∞ (n=number of Ru–O layers). With the layered nature of the crystal structures and the extended characteristic of the 4d-electrons, these ruthenates provide a truly unique opportunity to study not only the evolution of underlying physical properties as the dimensionality changes but also drastic transitions in ground states (localized antiferromanetism or itinerant ferromagnetism) when the cation (Ca or Sr) is replaced with each other. An enormous range of novel physical phenomena, which are manifested in transport and thermodynamic properties and believed to be fundamentally associated with the bad metallicity that characterizes these systems.