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Tunable Magnetic Scattering and Ferroelectric Switching at the LaAlO$_3$/EuTiO$_3$/Sr$_{0.99}$Ca$_{0.01}$TiO$_3$ Interface

Ferroelectric and ferromagnetic orders rarely coexist, and magnetoelectric coupling is even more scarce. A possible avenue for combining these orders is by interface design, where orders formed at the constituent materials can overlap and interact. Using a combination of magneto-transport and scanning SQUID measurements, we explore the interactions between ferroelectricity, magnetism, and the 2D electron system (2DES) formed at the novel LaAlO$_3$/EuTiO$_3$/Sr$_{0.99}$Ca$_{0.01}$TiO$_3$ heterostructure. We find that the electrons at the interface experience magnetic scattering appearing along with a diverging Curie-Weiss-type behaviour in the EuTiO$_3$ layer. The 2DES is also affected by the switchable ferroelectric polarization at the Sr$_{0.99}$Ca$_{0.01}$TiO$_3$ bulk. While the 2DES interacts with both magnetism and ferroelectricity, we show that the presence of the conducting electrons has no effect on magnetization in the EuTiO$_3$ layer. Our results provide a first step towards realizing a new multiferroic system where magnetism and ferroelectricity can interact via an intermediate conducting layer.