Suppression of An Antiferromagnetic Insulating Phase in Sr$_{3}$(Ru$_{1-x}$Mn$_{x})_{2}$O$_{7}$ by Magnetic Field*

Double-layered Sr$_{3}$Ru$_{2}$O$_{7 }$is a paramagnetic metal. The partial substitution of Mn for Ru results in metal-insulator transition at T$_{MIT}$ and antiferromagnetic ordering at T$_{M}$ in Sr$_{3}$(Ru$_{1-x}$Mn$_{x})_{2}$O$_{7. }$Interestingly, both T$_{MIT}$ and T$_{M}$ can be easily suppressed by the application of magnetic field, especially for low-doping compounds (x $<$ 0.1). This behavior can be explained as Mn-doping-induced antiferromagnetic-insulating domains below T$_{MIT}$. The application of magnetic field suppresses the antiferromagnetic coupling, thus converting the insulating domains back to metallic.