Distinguishing charge and strain coupling in ultrathin (001)-La0.7Sr0.3MnO3/PMN-PT heterostructures

Interfacial charge and strain distributions inside artificial perovskite ABO3 heterostructures often affect intriguing physical properties that are important to device performance. Normally, both charge and strain coexist across the interfaces, and their exact roles in determining the properties remain elusive. In the present work, La0.7Sr0.3MnO3 (LSMO) ultrathin films were grown on (001)-0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMNPT) single-crystal substrates to discriminate between the effect of charge and strain on the transport and magnetoelectric properties. In heterostructures with thicker LSMO films, the strain effect dominates the resistance and the magnetic moment depends on the external electric field. With the decreasing LSMO thickness, the butterfly-like resistance–electric-field (R-E) and magnetization–electric-field (M-E) curves become loop-like, indicating that charge effects dominate strain effects in determining the electric field that controls the transport and magnetic properties. Furthermore, soft-x-ray absorption spectra of 32 and 4 nm LSMO/PMNPT samples at the Mn L edge under an applied electric field of ±6 kV/cm indicate that orbital reconstruction also plays an important role in interfacial magnetoelectric coupling.