Doping-Induced Structural and Physical Properties Changes in Sr$_{3}$(Ru$_{1-x}$Mn$_{x})_{2}$O$_{7}$ Single Crystals

In the homologous strontium ruthenate series Sr$_{n+1}$Ru$_{n}$O$_{3n+1}$, double-layered Sr$_{3}$Ru$_{2}$O$_{7}$ exhibits unique physical properties. However, the partial substitution of Ru by the smaller Mn was found to change its ground state from a paramagnetic metal to an antiferromagnetic insulator with less distorted crystal structure. Interestingly, our Hall effect measurements show no change in the carrier concentration (x $\le $ 0.2), suggesting that Mn is isovalent with Ru in Sr$_{3}$(Ru$_{1-x}$Mn$_{x})_{2}$O$_{7}$. This is further supported by the magnetization data, which yield effective spin S = 3/2 for Mn corresponding to Mn$^{4+}$. In addition to bulk physical properties, the doping dependence of the surface structure and lattice dynamics of Sr$_{3}$(Ru$_{1-x}$Mn$_{x})_{2}$O$_{7}$ single crystals will be discussed.