ORCID Profile
0009-0001-9168-772X
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Publisher: AIP Publishing
Date: 27-09-2021
DOI: 10.1063/5.0062046
Abstract: Topological defects in ferroelectric materials have attracted much attention due to the emergence of conductive, ferroic, and magnetic functionalities. However, many topological configurations dynamically evolve during the switching processes, making them a challenge to characterize via traditional techniques. Here, we implement an automated experimentation approach for the exploration of functional properties in BiFeO3 thin films. Specifically, we visualize the ferroelectric domain structures via single frequency piezoresponse force microscopy and implement a computer vision-based algorithm to discover features of interest at which spectroscopic measurements are taken. Subsequently, we employ dimensionality reduction techniques to reveal characteristic polarization behaviors at these features. This approach can be extended to other spectroscopies and modalities to probe only specific features of interest, ultimately enabling dynamical processes in ferroelectrics to be studied.
Publisher: Wiley
Date: 06-04-2020
Publisher: Springer Science and Business Media LLC
Date: 23-09-2021
DOI: 10.1038/S41563-021-01098-W
Abstract: Piezoelectrics interconvert mechanical energy and electric charge and are widely used in actuators and sensors. The best performing materials are ferroelectrics at a morphotropic phase boundary, where several phases coexist. Switching between these phases by electric field produces a large electromechanical response. In ferroelectric BiFeO
Publisher: Springer Science and Business Media LLC
Date: 29-04-2019
DOI: 10.1038/S41535-019-0155-2
Abstract: Understanding and manipulating complex spin texture in multiferroics can offer new perspectives for electric field-controlled spin manipulation. In BiFeO 3 , a well-known room temperature multiferroic, the competition between various exchange interactions manifests itself as non-collinear spin order, i.e., an incommensurate spin cycloid with period 64 nm. We report on the stability and systematic expansion of the length of the spin cycloid in (110)-oriented epitaxial Co-doped BiFeO 3 thin films. Neutron diffraction shows (i) this cycloid, despite its partly out-of-plane canted propagation vector, can be stabilized in thinnest films (ii) the cycloid length expands significantly with decreasing film thickness (iii) theory confirms a unique [ $$11\\bar 2$$ 11 2 ¯ ] cycloid propagation direction and (iv) in the temperature dependence the cycloid length expands significantly close to T N . These observations are supported by Monte Carlo simulations based on a first-principles effective Hamiltonian method. Our results therefore offer new opportunities for nanoscale magnonic devices based on complex spin textures.
Publisher: Wiley
Date: 21-09-2020
Publisher: AIP Publishing
Date: 13-11-2019
DOI: 10.1063/1.5113530
Abstract: BiFeO3 thin films have attracted considerable attention by virtue of their potential application in low-energy spintronic and magnonic devices. BiFeO3 possesses an intricate magnetic structure, characterized by a spin cycloid with period ∼62 nm that governs the functional magnonic response, and which can be modulated or even destroyed by strain, magnetic and electric fields, or chemical doping. The literature on (110)-oriented BiFeO3 films is not explicit in defining the conditions under which this cycloid persists, as its presence depends on synthesis method and thin-film boundary conditions, especially in the sub-100 nm thickness regime. This report aims to end “trial and error” approaches in determining the conditions under which this cycloid and its associated functional magnonic response exist. We show that in specific crystallographic orientations of epitaxial BiFeO3, an unexplored strain parameter—the distortion in the ab plane of the monoclinic unit cell—significantly influences the spin structure. Combining Mössbauer spectroscopy and low-energy Raman spectroscopy with first-principles-based effective Hamiltonian calculations, we show that both average strain and this distortion destroy the cycloid. For films grown on (110)-oriented SrTiO3 substrates, if the BiFeO3 lattice parameters a and b differ by more than about 1.2%, the cycloid is destabilized, resulting in a pseudocollinear magnetic order ground state. We are thereby able to construct a phase diagram of the spin structure for nanoscale epitaxial BiFeO3 films, which aims to resolve long-standing literature inconsistencies and provide powerful guidelines for the design of future magnonic and spintronic devices.
Publisher: American Physical Society (APS)
Date: 09-03-2021
Publisher: Wiley
Date: 19-01-2023
Abstract: A review of the applications of polarized neutron reflectometry (PNR) for the investigation of quantum materials is provided. Recent studies of superconductors, strongly correlated oxides, hydrogen‐induced modifications, topological insulators and chiral magnets are highlighted. The PNR technique uses a quantum beam of spin‐polarized neutrons to measure the nanomagnetic structure of thin films and heterostructures, with a sensitivity to magnetization at the scale of 10–2000 emu cm −3 and a vertical spatial resolution of 1–500 nm. From simple beginnings studying the magnetic flux penetration at superconducting surfaces, today the PNR technique is widely used for investigating many different types of thin film structures, surfaces, interfaces, and 2D materials. PNR measurements can reveal a number of details about magnetic, electronic, and superconducting properties, in tandem with chemical information including the stoichiometry of light elements such as oxygen and hydrogen.
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