Study Of Magnetoelectric Effects In Multiferroic Composite Thin Films

Multiferroic materials not only have all kinds of single ferroics （such asferroelectricity, ferromagnetism and ferroelasticity）, but also can produce some newfunctions （e.g., magnetoelectric coupling effects） due to the coupling synergy betweenferroelectricity and ferromagnetism, which greatly broadens the application ofmultiferroic materials. Recently, Multiferroic magnetoelectric composite systems suchas ferromagnetic-ferroelectric heterostructures have recently attracted anever-increasing interest and provoked a great number of research activities, driven byprofound physics from coupling between ferroelectric and magnetic orders, as well aspotential applications in novel multifunctional devices, such as sensors, transducers,memories, and spintronics. In this paper, we investigated in detail the magnetoelectriccoupling properties of multiferroic composite thin films ofPb(Zr_0.52,Ti_0.48)O₃-La_0.65Sr_0.65MnO₃and Bi_3.15Nd_0.85TiO₃-La_0.7Ca_0.3MnO₃. The2-2type epitaxial heterostructures and0-3type nanocomposite thin films show a robustmagnetoelectric effects by the measurement of magnetic field induced ferroelectricpolarization.The magnetoelectric （ME） PZT-LSMO composite thin films were grown onsingle crystalline SrTiO₃substrates by the pulse laser deposition （PLD） method withdifferent growth sequences of PZT and LSMO yielding the following layeredstructures: PZT/LSMO/substrate （PL） and LSMO/PZT/substrate （LP）. Theexperimental results show that multiferroic thin films simultaneously exhibit superbferroelectric and magnetic properties, which also possess the fantastic magnetoelectriceffects at room temperature. The layer sequences have an obvious influence on themagnetoelectric coupling behavior of these double-layered thin films. The maximumvalues of ME voltage coefficient for the PL thin film is larger than the LP structure,which may be caused by the substrate clamping and interface bonding of PZT andLSMO.（1-x）BNT-xLCMO(x=_0.3,0.4,0.5) composite thin films were fabricated onPt/Ti/SiO₂/Si substrates by a chemical solution deposition method. The well-definedferroelectric loops are observed. The Prvalues are11.2,12.8, and13.9μC/cm2underthe condition of about350kV/cm electric field for the composite films with x=_0.3,0.4, and0.5. The composite films exhibit typical magnetic hysteresis loops, as well as remnant magnetizations. ME effect which is dependent on Hbiasis observed. Theresults show that these composite films concurrently show good ferroelectric andferromagnetic properties, as well as a ME effect.