Spatially Modulated Magnetic Structure EuS Due to the Tetragonal Domain Structure of SrTiO3
The combination of magnetic order with systems such as topological superconductors or insulators allows for new types of excitations such as chiral edge modes or majorana fermions. SrTiO3 (STO) has been a versatile platform for growing the materials behind these proposals. EuS is a wide-band- gap ferromagnetic semiconductor that could provide a new route toward realizing these more exotic phases. We present scanning SQUID measurements of EuS epitaxially grown on STO and observe micron-scale features in ferromagnetism and paramagnetism at low temperatures. The features are oriented along the STO crystal axes and only change their configuration upon thermal cycling above the STO cubic to tetragonal structural transition temperature. These observations suggest that the observed magnetic features are due to coupling between EuS and the low temperature STO tetragonal structure. This result demonstrates that local variation in the induced magnetic order from EuS grown on STO needs to be considered when engineering new phases that require isotropic exchange coupling.