Strain and electric field control of magnetism in La(1--x)SrxMnO3 thin films on ferroelectric BaTiO3 substrates

Abstract

We report on the observation of strain- and magneto-electric coupling in a system consisting of a thin film of ferromagnetic La(1−x)SrxMnO3 (LSMO, x = 0.5 and 0.3) on a ferroelectric BaTiO3 (BTO) substrate. Pronounced magnetization steps occur at the BTO structural phase transitions. We associate these steps with a strain induced change of the magnetic anisotropy. Temperature dependent magneto-electric coupling could be evidenced by the magnetic response to an applied AC electric field in all ferroelectric phases of the BTO substrate. In a DC electric field, the magnetization changes are asymmetric with respect to the polarity. Polarized neutron reflectometry hints to oxygen migration as possible mechanism for this asymmetry. It also reveals strain-induced magnetization changes throughout most of the thickness of 252 Å (x = 0.5) and 360 Å (x = 0.3), respectively, of the LSMO layer. We conclude that the change of the magnetization depth profile at the interface as previously proposed by ab initio calculations is not the relevant mechanism. Instead strain, oxygen vacancies and frustration at interfacial steps dominate the magnetic response to an applied electric field.