Effect of lattice mismatch on the magnetic properties of nanometer-thick La _0.9 Ba _0.1 MnO ₃ (LBM) films and LBM/BaTiO ₃ /LBM heterostructures

Oxide multiferroic thin films and heterostructures offer a wide range of properties originated from intrinsic coupling between lattice strain and nanoscale magnetic/electronic ordering. La _0.9 Ba _0.1 MnO ₃ (LBM) thin-films and LBM/BaTiO ₃ /LBM (LBMBT) heterostructures were grown on single crystalline [100] silicon and [0001] Al ₂ O ₃ using RF magnetron sputtering to study the effect of crystallinity and induced lattice mismatch in the film on magnetic properties of deposited films and heterostructures. The thicknesses of the films on Al ₂ O ₃ and Si are 70 and 145 nm, respectively, and for heterostructures are 40/30/40 nm on both substrates. The microstructure of the films, state of strain and growth orientations was studied by XRD and microscopy techniques. Interplay of microstructure, strain and magnetic properties is further investigated. It is known that the crystal structure of substrates and imposed tensile strain affect the physical properties; i.e. magnetic behavior of the film. The thin layer grown on Al ₂ O ₃ substrate shows out-of-plane compressive strain, while Si substrate induces tensile strain on the deposited film. The magnetic transition temperatures (T _c ) of the LBM film on the Si and Al ₂ O ₃ substrates are found to be 195 K and 203 K, respectively, slightly higher than the bulk form, 185 K. The LBMBT heterostructure on Si substrate shows drastic decrease in magnetization due to produced defects created by diffusion of Ti ions into magnetic layer. Meanwhile, the T _c in LBMBT _s increases in respect to other studied single layers and heterostructure, because of higher tensile strain induced at the interfaces.