Commensurate-incommensurate magnetic phase transition in the Fe-doped bilayer ruthenate Ca3Ru2 O7

Neutron diffraction studies have revealed an uncommon commensurate- incommensurate magnetic phase transition with decreasing temperature in the (∼5%) Fe-doped bilayer ruthenate Ca3(Ru,Fe)2O7. An incommensurate phase formed of a cycloidal spiral spin structure coexists with a commensurate one below the phase transition at 42 K and persists down to the lowest temperature, accompanied by higher-order magnetic satellite peaks which indicate the formation of a magnetic soliton lattice. We ascribe these findings to the competing magnetic interactions in this system. This study demonstrates an effective approach to tune novel magnetic and electronic properties of ruthenates via 3d magnetic transition-metal substitution.