Self-Poling-Induced Magnetoelectric Effect in Highly Strained Epitaxial BiFeO 3 /La 0.67 Sr 0.33 MnO 3-δ Multiferroic Heterostructures.

Highly strained epitaxial BiFeO3 /La0.67 Sr0.33 MnO3-δ (BFO/LSMO) heterostructures were fabricated on LaAlO3 substrates by magnetron sputtering. The as-grown downward self-polarization of BFO capping layers was confirmed by piezoelectric force microscopy. Using the electrostatic field-induced charge screening, a hole depletion state was induced in ultrathin (8 nm) LSMO films. As a result of the interfacial charge coupling, appreciable saturated magnetization (MS ) increase of about 500 and 100% can be observed in LSMO with BFO capping at 5 and 300 K, respectively. Besides, LSMO phase translations can be revealed by the BFO thickness-related exchange bias field (HE ) and MS of the BFO/LSMO heterostructures. The results established a new approach in achieving interfacial magnetoelectric couplings with thin self-polarized multiferroic layers.