Carrier Density Control of Magnetism and Berry Phases in Doped EuTiO3
Kaveh Ahadi, Zhigang Gui, Zach Porter, Jeffrey W. Lynn, Zhijun NMN Xu, Stephen D. Wilson, Anderson Janotti, Susanne Stemmer
In materials with broken time-reversal symmetry, the Berry curvature acts as a reciprocal space magnetic field on the conduction electrons and is significant contribution to the magnetotransport properties, including to the intrinsic anomalous Hall effect. Here, we report neutron diffraction, transport and magnetization measurements of thin films of doped EuTiO3, an itinerant magnetic material, as a function of carrier density and magnetic field. These films are itinerant antiferromagnets at all doping concentrations. At low carrier densities, the magnetoresistance indicates a metamagnetic transition, which is absent at high carrier densities (>6x1020 cm-3). Strikingly, the crossover coincides with a sign change in the spontaneous Hall effects, indicating a sign change in the Berry curvature. We discuss the results in the context of the band structure topology and its coupling to the magnetic texture.