Browsing NTNU Open by Author "Grepstad, Jostein"
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Anisotropy and domain formation in a dipolar magnetic metamaterial
Digernes, Einar Standal; Strømberg, Anders; Vaz, Carlos A. F.; Kleibert, Armin; Grepstad, Jostein; Folven, Erik (Journal article; Peer reviewed, 2021) -
Antiferromagnetic Domain Contrast in LaFeO3 Thin Films: Examined with X-ray Magnetic Linear Dichroism and Photo Electron Emission Microscopy
Kristiansen, Tom (Master thesis, 2006)This study will focus on strain induced by thermal history and thickness on antiferromagnetic epitaxial LaFeO3(110) thin films grown on Nb:SrTiO3(001) substrates. Lattice mismatching between film and substrate induce strain ... -
Controlling the switching field in nanomagnets by means of domain-engineered antiferromagnets
Folven, Erik; Linder, Jacob; Gomonay, Helen V.; Scholl, Andreas; Doran, Andrew; Young, Anthony; Retterer, Scott; Malik, V.K.; Tybell, Per Thomas Martin; Takamura, Yayoi; Grepstad, Jostein (Journal article, 2015)Using soft x-ray spectromicroscopy, we investigate the magnetic domain structure in embedded nanomagnets defined in La0.7Sr0.3MnO3 thin films and LaFeO3/La0.7Sr0.3MnO3 bilayers. We find that shape-controlled antiferromagnetic ... -
Crystalline symmetry controlled magnetic switching in epitaxial (111) La0.7Sr0.3MnO3 thin films
Hallsteinsen, Ingrid; Folven, Erik; Olsen, Fredrik Kjemperud; Chopdekar, R.V.; Rzchowski, M; Eom, C.B.; Grepstad, Jostein; Tybell, Per Thomas Martin (Journal article; Peer reviewed, 2015)Mixed-valence manganite thin films are attractive for spintronic devices. Crystalline orientation is a promising route to tailor switching mechanisms, as magnetization reversal depends on the magnetic anisotropy. Here, ... -
Direct imaging of long-range ferromagnetic and antiferromagnetic order in a dipolar metamaterial
Digernes, Einar; Slöetjes, Samuel Dingeman; Strømberg, Anders; Bang, Ambjørn Dahle; Olsen, Fredrik Kjemperud; Arenholz, Elke; Chopdekar, Rajesh V.; Grepstad, Jostein; Folven, Erik (Journal article, 2020)Magnetic metamaterials such as artificial spin ice offer a route to tailor magnetic properties. Such materials can be fabricated by lithographically defining arrays of nanoscale magnetic islands. The magnetostatic interactions ... -
Effect of surface roughness, chemical composition, and native oxide crystallinity on the orientation of self-assembled GaN nanowires on Ti foils
Calabrese, G; Pettersen, Sverre Vegard; Pfuller, C; Ramsteiner, M; Grepstad, Jostein; Brandt, O; Geelhaar, L; Fernandez-Garrido, S (Journal article; Peer reviewed, 2017)We report on plasma-assisted molecular beam epitaxial growth of almost randomly oriented, uniformly tilted, and vertically aligned self-assembled GaN nanowires (NWs), respectively, on different types of polycrystalline Ti ... -
Effects of array shape and disk ellipticity in dipolar-coupled magnetic metamaterials
Slöetjes, Samuel Dingeman; Digernes, Einar; Strømberg, Anders; Olsen, Fredrik Kjemperud; Bang, Ambjørn Dahle; N'diaye, Alpha T; Chopdekar, Rajesh V.; Folven, Erik; Grepstad, Jostein (Peer reviewed; Journal article, 2021)Two-dimensional lattices of dipolar-coupled thin film ferromagnetic nanodisks give rise to emergent superferromagnetic (SFM) order when the spacing between dots becomes sufficiently small. In this paper, we define micron-sized ... -
Effects of lattice geometry on the dynamic properties of dipolar-coupled magnetic nanodisk arrays
Slöetjes, Samuel Dingeman; Digernes, Einar; Klewe, Christoph; Shafer, Padraic; Li, Qian; Yang, M.; Qiu, Z.Q.; N'diaye, Alpha T; Arenholz, Elke; Folven, Erik; Grepstad, Jostein (Journal article; Peer reviewed, 2019)We have studied the impact of lattice geometry on the dynamic properties of close-spaced arrays of circular nanomagnets, also known as magnonic crystals. To this end, we prepared 2D nanomagnet arrays with both square and ... -
Effects of substrate annealing on the gold-catalyzed growth of ZnO nanostructures
Weigand, Christian Carl; Skåre, Daniel; Ladam, Cecile; Grepstad, Jostein; Weman, Helge (Journal article; Peer reviewed, 2011)The effects of thermal substrate pretreatment on the growth of Au-catalyzed ZnO nanostructures by pulsed laser deposition are investigated. C-plane sapphire substrates are annealed prior to deposition of a thin Au layer. ... -
Enhanced magnetic signal along edges of embedded epitaxial La0.7Sr0.3MnO3 nanostructures
Olsen, Fredrik Kjemperud; Bang, Ambjørn Dahle; Digernes, Einar; Slöetjes, Samuel Dingeman; Andreas, Scholl; Chopdekar, Rajesh V.; Tybell, Per Thomas Martin; Grepstad, Jostein; Folven, Erik (Peer reviewed; Journal article, 2020)When thin films are patterned to realize nanoscale device geometries, maintaining their structural integrity is key to the quality of their functional properties. The introduction of new surfaces and interfaces by lateral ... -
Exchange explosions of topological edge defects in a square micromagnet
Slöetjes, Samuel Dingeman; Folven, Erik; Grepstad, Jostein (Peer reviewed; Journal article, 2020)) with a flux-closure magnetic ground state were investigated by micromagnetic simulations. The system was excited with an applied magnetic field, displacing the vortex core sufficiently far from its equilibrium position ... -
Exploring the Antiferromagnetic Spin Configuration in Complex Oxide Nanostructures
Bang, Ambjørn Dahle (Doctoral theses at NTNU;2020:58, Doctoral thesis, 2020)Improving energy efficiency is an urgent priority for the device technologies of tomorrow. To this end, introduction of spintronic devices where antiferromagnetic spins play an active role is a promising avenue, offering ... -
Fabrication and characterization of optical waveguide components in epitaxial (Pb,La)(Zr,Ti)O3 thin films.
Kjellman, Jon Øyvind (Master thesis, 2009)This report presents a method for fabrication of ridge-type waveguide electro-optic modulators in 500 nm thick, c-oriented, epitaxial, (Pb0.92,La0.08)(Zr0.4,Ti0.6)O3 thin films on a MgO substrate. The method is based on ... -
Improved Induced Diode Photodetectors by Increased Fixed Charge in PECVD Amorphous Silicon Nitride
Bazilchuk, Molly Strimbeck (Master thesis, 2014)The predictable quantum efficient detector (PQED) is a cheaper, more practical alternative to the current radiometric primary standard, the cryogenic radiometer. The PQED is made of an induced diode, a rectifying junction ... -
In-plane structural order of domain engineered La0.7Sr0.3MnO3 thin films
Boschker, Jos Emiel; Monsen, Åsmund Fløystad; Nord, Magnus Kristofer; Mathieu, Roland; Grepstad, Jostein; Holmestad, Randi; Wahlström, Erik; Tybell, Thomas (Journal article, 2013)We present a detailed structural study of tensile-strained La0.7Sr0.3MnO3 thin films. We use the substrate miscut to control the number of rhombohedral variants in the films and study the in-plane order and structural ... -
Individual Strings of Conducting Carbon Particles in Polymer Matrix: Electric Field Induced Preparation and Electromechanical Properties
Høyer, Henrik (Master thesis, 2011)In this report, a novel method for making single strings of particles is presented.These strings were characterized using diverse electromechanical methods -
Interplay between bulk and edge-bound topological defects in a square micromagnet
Slöetjes, Samuel Dingeman; Digernes, Einar; Olsen, Fredrik Kjemperud; Chopdekar, Rajesh V.; Retterer, Scott T.; Folven, Erik; Grepstad, Jostein (Journal article; Peer reviewed, 2018)A field-driven transformation of a domain pattern in a square micromagnet, defined in a thin film of La0.7Sr0.3MnO3, is discussed in terms of creation and annihilation of bulk vortices and edge-bound topological defects ... -
Large Area Patterning of Embedded Magnetic Nanostructures in Complex Oxide Thin Films
Mellbye, Aksel Skauge (Master thesis, 2015)Complex oxide materials exhibit a wide range of functional properties, making them interesting for future use in electronic and spintronic devices. Through nanopatterning of thin film structures, magnetic shape effects can ... -
Magnetic domain configuration of (111)-oriented LaFeO3 epitaxial thin films
Hallsteinsen, Ingrid; Moreau, Magnus; Chopdekar, R.V.; Christiansen, Emil; Nord, Magnus Kristofer; Vullum, Per Erik; Grepstad, Jostein; Holmestad, Randi; Selbach, Sverre Magnus; Scholl, A; Arenholz, E; Folven, Erik; Tybell, Per Thomas Martin (Journal article; Peer reviewed, 2017)In antiferromagnetic spintronics control of the domains and corresponding spin axis orientation is crucial for devices. Here we investigate the antiferromagnetic axis in (111)-oriented LaFeO3/SrTiO3, which is coupled to ... -
Magnetic domain formation in ultrathin complex oxide ferromagnetic/antiferromagnetic bilayers
Bang, Ambjørn Dahle; Olsen, Fredrik Kjemperud; Slöetjes, Samuel Dingeman; Scholl, Andreas; Retterer, Scott T.; Vaz, Carlos; Tybell, Per Thomas Martin; Folven, Erik; Grepstad, Jostein (Journal article; Peer reviewed, 2018)In this study, we report on the magnetic domain formation in ultrathin blanket films and patterned micro- and nanostructures of ferromagnetic (FM) La0.7Sr0.3MnO3 single-layers and antiferromagnetic (AF)/ferromagnetic ...