Manipulating magnetism inLa0.7Sr0.3MnO3via piezostrain

Abstract

We present a detailed study of the ferromagnetic/ferroelectric heterostructure ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}/{[\mathrm{Pb}({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}]}_{0.68}\ensuremath{-}{[{\mathrm{PbTiO}}_{3}]}_{0.32}$ (011), where reversible electrical switching induces a 10 K shift of the magnetic Curie temperature ${\mathrm{T}}_{C}$. Two distinct polarization configurations can be set in the ferroelectric substrate and are stable at remanence; reciprocal space maps highlight the accompanying lattice parameter changes which impose a biaxial strain on the manganite thin film. The magnetic response to the strain changes is probed by temperature dependent Mn ${L}_{3,2}$ x-ray magnetic circular dichroism and resistance measurements. X-ray natural linear dichroism spectra for both strain states probe the valence charge anisotropy: The existing population imbalance between out-of-plane and in-plane oriented orbitals increases further with tensile strain, favoring orbital occupation in the surface plane. Multiplet and density functional theory calculations support the emerging picture that an increase in tensile in-plane strain leads to an increased energy difference between the two $\mathrm{e}{}_{g}$ orbitals and a larger Mn-O-bond length. Increasing the electron-lattice coupling and reducing the $\mathrm{e}{}_{g}$ electron itinerancy that leads to ferromagnetism due to double exchange coupling, results ultimately in lower ${\mathrm{T}}_{C}$ values.