Antiferromagnetic Metallic State And Spin Valve Effect in Doped (Ca$_{1-x}$ A$_{x})_{3}$Ru$_{2}$O$_{7}$ (A = Sr, Ba) Single Crystals

Bilayered Ca$_{3}$Ru$_{2}$O$_{7}$ is a highly anisotropic system [1] characterized by orbitally-driven colossal magnetoresistance$^{2}$ and an unusual antiferromagnetic metallic (AFM-M) state [2]. We report transport and thermodynamic properties of (Ca$_{1-x}$ A$_{x})_{3}$Ru$_{2}$O$_{7}$ (A = Sr, Ba) single crystals as a function of temperature and applied magnetic field. While Ba doping shows a far stronger impact, both Sr and Ba substitution for Ca induce a large array of interesting phenomena. Among them, a bulk spin-valve effect occurs in the AFM-M range, which is largely broadened due to the doping. This effect in bulk crystals is a novel phenomenon first observed in Ca$_{3}$(Ru$_{1-x}$Cr$_{x})_{2}$O$_{7}$ single crystals [3]. The spin-valve effect in (Ca$_{1-x}$A$_{x})_{3}$Ru$_{2}$O$_{7}$ single crystals opens new avenues to understand the underlying physics and realize the potential of spin valves in practical devices.\\[0pt] [1] G. Cao et al., \textit{PRL} \textbf{78}, 1751 (1997)\\[0pt] [2] X. N. Lin et al., \textit{PRL} \textbf{95}, 017203 (2005)\\[0pt] [3] G. Cao et al., \textit{PRL} \textbf{100}, 016604 (2008)