Room-temperature dilute ferromagnetic dislocations in Sr1−xMnxTiO3−δ

Room-temperature dilute ferromagnetism has been reported for many semiconducting or insulating materials, which are usually in the forms of bulk or thin film. Here, we successfully fabricated dilute ferromagnetic nanowires by using dislocations---one-dimensional lattice defects---embedded between optically transparent, nonmagnetic $\mathrm{SrTi}{\mathrm{O}}₃$ single crystals. At the dislocation cores, we have both locally codoped magnetic $\mathrm{M}{\mathrm{n}}²⁺$ ions and electron donors. The structure, chemistry, and ferromagnetism of dislocations were studied by atomic-resolution scanning transmission electron microscopy combined with magnetic force microscopy. We discuss the origin of dilute ferromagnetism at the dislocations in terms of the percolation of bound magnetic polarons along the dislocation cores, where antiferromagnetic coupling between the high spin state of $\mathrm{M}{\mathrm{n}}²⁺$ ions and electron donors leads to the long-range Mn-Mn ferromagnetic exchange interaction.