Simulation of Hall sign change in ferromagnet SrRuO3*

We employed a modified two-band model to theoretically investigate the mechanism of Hall sign change in SrRuO3, in which an mpurity band couple with conduction and valence bands. Apparently, our theory can interpret the experimental results, which implies the proposed impurity band arising from Ru vacancies is an important factor in Hall sign change. We found that the electron density in the impurity band is getting increase as the impurity band energy approaches the chemical potential resulting in a decrease of Curie temperature of SrRuO3. Besides, the Hall sign change occurs at the Curie temperature only when the band oupling is weak. Further more, the increase of the Ru vacancies makes the impurity band become solid but suppress the Curie temperature. Moreover, from the theoretical prediction a more relatively intrinsic p-type SrRuO3 has higher Curie temperature and opposite for intrinsic n-type SrRuO3.