Download or read book Epitaxial Strain, Electric Field, and Domains Controlled Functionality Modulations in Complex Oxide Heterostructures written by Binod Paudel and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The perovskite 3d- transitional metal complex oxides offer opportunities to construct artificial heterostructures and chemical doping of atoms with different atomic radii resulting in similar crystal structures but diverse functionalities. The discovery of such functionalities has been possible because of the advances in synthesis, which enables fabrication of oxide heterostructures in the form of thin films, thus providing a rich ground to study their functional response with external stimuli, such as strain, electric field, and chemical pressure. In this dissertation, I investigate how such parameters can modulate different functionalities magnetic (interfacial and bulk), transport, and optical, in the three-class of heterostructures, namely: lightly doped manganite, multiferroic heterostructures, and rare-earth chromites.In the first work, I study the magneto-electric coupling at the heterostructure interface of a ferroelectric PbZr0.2Ti0.8O3 (PZT) and ferromagnetic La0.67Sr0.33MnO3 (LSMO) layers grown on an Nb-doped SrTiO3 (001) substrate utilizing polarized neutron reflectometry (PNR) in consort with ab initio-based density functional theory (DFT) calculations. The working conditions of the functional device are mimicked by gating the heterostructure with a Pt top electrode to apply an external electric field, which alters the magnitude and switches the direction of the ferroelectric (FE) polarization, across the PZT layer. PNR results show that the gated PZT/LSMO exhibits interfacial magnetic phase modulation attributed to ferromagnetic (FM) to A-antiferromagnetic (A-AF) phase transitions resulting from the accumulation of holes. When the net FE polarization points towards the interface (positive), the interface does not undergo a magnetic phase transition and retains its global FM-ordered state. In addition to changes in the interfacial magnetic ordering, the global magnetization of LSMO increases. while switching the polarization from positive to negative and it decreases vice versa. DFT calculations indicate that this enhanced magnetization also correlates with an out-of-plane tensile strain, whereas the suppressed magnetization for positive polarization is attributed to out-of-plane compressive strain. These calculations also show the coexistence of FM and A-AF -phases at zero out of plane strain. Charge modulations throughout the LSMO layer appear to be unaffected by strain, suggesting that these charge-mediated effects do not significantly change the global magnetization. Such results verify that the interfacial magnetic modulations are due to co-action of strain- and charge-mediated effects, which dominate at different length scales. In the second work, I study the microstructural evolution induced magnetism and transport properties of ferroelastic La0.9Sr0.1MnO3 (LSMO) epitaxial thin films grown on SrTiO3 (001) substrates with different miscut angles. The substrate miscut angle plays a critical role in controlling the in-plane magnetic anisotropy. The microscopic origin of such magnetic anisotropy is attributed to the formation of anisotropic stripe domains along the step terraces at the surface. The Curie temperature is found to be decreased and magnetoresistance gradually increases with the increase in miscut angles. The magnetization in the LSMO films was found to be selectively modulated by the antiferrodistortive phase transition of the SrTiO3 substrate. This phenomenon has been qualitatively explained by a strain-modified Stoner–Wohlfarth model. We conclude that the magnetization modulation by the SrTiO3 phase transition depends on h, the ratio of the applied magnetic field to the saturation field. Such modulation is only visible with h