Magnetic Interactions in Strained Multiferroic EuTiO$_3$ Thin Films

Bulk EuTiO$_3$ possesses a paraelectric and antiferromagnetic ground but it has been predicted that under tensile strain the system would show spontaneous ferromagnetic and ferroelectric order[1]. Here we present a study of the magnetic interactions in thin films of EuTiO$_3$ grown on SrTiO$_3$(001) and DyScO$_3$(110) substrates by reactive molecular-beam epitaxy (MBE). Using magnetometry, x-ray magnetic circular dichroism, and magneto-capacitance, there clear evidence of ferromagnetic order under tensile strain while the unstrained films are anti-ferromagnetic. These results will be discussed in the context of the predicted behavior. Work at Argonne, including the Advanced Photon, is supported by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. [1] C.J. Fennie and K.M. Rabe, Phys. Rev. Lett. 97, 267602 (2006)].