We report the observation of room temperature ferromagnetism in high quality, single crystalline dilute Fe-doped $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_3$. The large equilibrium solubility of Fe ions in the matrix refutes uncertainties about secondary phase magnetism, which has often eclipsed this interesting field of research. While room temperature ferromagnetism is observed at and above 5% Fe concentrations, one finds a highly concave temperature dependence of the susceptibility. Using detailed ab initio calculation, this has been related to intrinsic magnetic inhomogeneities arising from positional disorder. Apart from providing a mechanism for the observed high temperature ferromagnetism, our results point out that intrinsic disorder is a generic and essential component of dilute magnetism.

• Received 7 November 2007

DOI:https://doi.org/10.1103/PhysRevB.77.104416