Optical Characterization of Interface Magnetization in Multifunctional Oxide Heterostructures - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Optical Characterization of Interface Magnetization in Multifunctional Oxide Heterostructures write by Fan Fang (Ph.D.). This book was released on 2016. Optical Characterization of Interface Magnetization in Multifunctional Oxide Heterostructures available in PDF, EPUB and Kindle. Multifunctional oxides attract much attention recently. The strong correlated electron system involves the notable properties of colossal magnetoresistance, ferroelectric tunneling and spin transport, with the coupling of electron, spin and orbital degrees of freedom. Their rich functional behavior is of potential use for nanoelectronics and data storage. Particularly interesting are the mulitferroic materials, which exhibit simultaneously electric and magnetic ordering properties. Understanding the interface coupling mechanism of these two order parameters are critical to future development of high-performance spintronic devices. The goal of this dissertation is to elucidate the interfacial magnetoelectric (ME) coupling with optical characterization method -- magnetization-induced second-harmonic generation (MSHG), which is sensitive to the interface due to the broken spatial inversion symmetry. First, ME coupling at the interface of BaTiO3 (BTO)/La0.67Sr0.33MnO3 (LSMO) is observed by applying an external electric field. The voltage-dependent magnetic contrast reveals a sharp transition from ferromagnetic (FM) to antiferromagnetic (AFM) order occurring at positive voltage (applied to LSMO contact). This novel effect is attributed to interface ME coupling. Strain or ferroelectric (FE) polarization induced mechanisms do not play an important role in this system. A new mechanism is proposed -- minority spin injection -- to modulate the interface magnetization. The minority spin injection at the interface weakens the double-exchange coupling of nearby eg electrons, thereby weakening the FM ordering. Thus the dominant AFM superexchange coupling of localized t2g electrons causes the phase transition at positive voltage. The magnetic transition is shifted to higher voltage by reducing the carrier concentration of BTO. Second, a non-multiferroic heterostructure -- SrTiO3 (STO)/La0.5Ca0.5MnO3 (LCMO)/La0.67Sr0.33MnO3 (LSMO) -- is studied to elucidate further the interface ME effect. The magnetization transition is observed but shifted to negative voltage. The LSMO is pushed to higher hole doping level due to the STO layer which acts as a hole donating layer, while the LCMO interlayer at the medium doping level displays complicated CE-type AFM phase. Thus, a negative voltage is required to lower the hole doping level of LSMO to induce the FM phase. The magnetic contrast reappears at high positive voltage, indicating the occurrence of an A-type AFM phase, which is stable at high hole doping concentration. The results of this dissertation show that the interface magnetic phase of LSMO can be controlled by an applied electric field through modulation of the hole doping level.
Optical Characterization of Ferromagnetic Heterostructure Interfaces and Thin Films
Optical Characterization of Ferromagnetic Heterostructure Interfaces and Thin Films - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Optical Characterization of Ferromagnetic Heterostructure Interfaces and Thin Films write by Haibin Zhao. This book was released on 2006. Optical Characterization of Ferromagnetic Heterostructure Interfaces and Thin Films available in PDF, EPUB and Kindle.
Multifunctional Oxide Heterostructures
Multifunctional Oxide Heterostructures - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Multifunctional Oxide Heterostructures write by Evgeny Y. Tsymbal. This book was released on 2012-08-30. Multifunctional Oxide Heterostructures available in PDF, EPUB and Kindle. This book is devoted to the rapidly developing field of oxide thin-films and heterostructures. Oxide materials combined with atomic-scale precision in a heterostructure exhibit an abundance of macroscopic physical properties involving the strong coupling between the electronic, spin, and structural degrees of freedom, and the interplay between magnetism, ferroelectricity, and conductivity. Recent advances in thin-film deposition and characterization techniques made possible the experimental realization of such oxide heterostructures, promising novel functionalities and device concepts. The book consists of chapters on some of the key innovations in the field over recent years, including strongly correlated oxide heterostructures, magnetoelectric coupling and multiferroic materials, thermoelectric phenomena, and two-dimensional electron gases at oxide interfaces. The book covers the core principles, describes experimental approaches to fabricate and characterize oxide heterostructures, demonstrates new functional properties of these materials, and provides an overview of novel applications.
Correlating Interfacial Structure and Magnetism in Thin-Film Oxide Heterostructures Using Transmission Electron Microscopy and Polarized Neutron Reflectometry
Correlating Interfacial Structure and Magnetism in Thin-Film Oxide Heterostructures Using Transmission Electron Microscopy and Polarized Neutron Reflectometry - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Correlating Interfacial Structure and Magnetism in Thin-Film Oxide Heterostructures Using Transmission Electron Microscopy and Polarized Neutron Reflectometry write by Steven Richard Spurgeon. This book was released on 2014. Correlating Interfacial Structure and Magnetism in Thin-Film Oxide Heterostructures Using Transmission Electron Microscopy and Polarized Neutron Reflectometry available in PDF, EPUB and Kindle. Oxide thin-films have attracted considerable attention for a new generation of spintronics devices, where both electron charge and spin are used to transport information. However, a poor understanding of the local features that mediate magnetization and coupling in these materials has greatly limited their deployment into new information and communication technologies. This thesis describes direct, local measurements of structure-property relationships in ferrous thin-films and La1-xSrxMnO3 (LSMO) / Pb(ZrxTi1-x)O3 (PZT) thin-film heterostructures using spatially-resolved characterization techniques. In the first part of this thesis we explore the properties of ferrous spintronic thin-films. These films serve as a model system to establish a suite of interfacial characterization techniques for subsequent studies. We then study the static behavior of LSMO / PZT devices with polarization set by the underlying substrate. Using transmission electron microscopy and geometric phase analysis we reveal the presence of significant local strain gradients in these films for the first time. Electron energy loss spectroscopy mapping of the LSMO / PZT interface reveals Mn valence changes induced by charge-transfer screening. Bulk magnetometry and polarized neutron reflectometry indicate that these chemical and strain changes are associated with a graded magnetization across the LSMO layer. Density functional theory calculations are presented, which show that strain and charge-transfer screening act locally to suppress magnetization in the LSMO by changing the Mn orbital polarization. In the second half of this thesis, we explore asymmetric screening effects on magnetization LSMO / PZT composites. We find that the local ferroelectric polarization can vary widely and that this may be responsible for reduced charge-transfer effects, as well as magnetic phase gradients at interfaces. From this information and electron energy loss spectroscopy, we construct a map of the magnetic phases at the interface. Collectively these results show that we must move toward high-resolution local probes of structure and magnetism to achieve deterministic control of functional thin-film oxides.
Optical Characterization of Ferromagnetic and Multiferroic Thin-film Heterostructures
Optical Characterization of Ferromagnetic and Multiferroic Thin-film Heterostructures - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Optical Characterization of Ferromagnetic and Multiferroic Thin-film Heterostructures write by Xin Ma (Ph. D.). This book was released on 2015. Optical Characterization of Ferromagnetic and Multiferroic Thin-film Heterostructures available in PDF, EPUB and Kindle.
