Leidy Marcela Giraldo Castaño


Last Name

Giraldo Castaño

First Name

Leidy Marcela

ORCID

0000-0002-4577-9949

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2017 - 201922020 - 20244
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Publications 1 - 6 of 6
  • Coexistence of Bloch and Néel walls in a collinear antiferromagnet
    Item type: Journal Article
    Wörnle, Martin S.; Welter, Pol; Giraldo Castaño, Leidy Marcela; et al. (2021)
    Physical Review B
    We resolve the domain-wall structure of the model antiferromagnet Cr2O3 using nanoscale scanning diamond magnetometry and second-harmonic-generation microscopy. We find that the 180° domain walls are predominantly Bloch-like, and can coexist with Néel walls in crystals with significant in-plane anisotropy. In the latter case, Néel walls that run perpendicular to a magnetic easy axis acquire a well-defined chirality. We further report quantitative measurement of the domain-wall width and surface magnetization. Our results provide fundamental input and an experimental methodology for the understanding of domain walls in pure, intrinsic antiferromagnets, which is relevant to achieve electrical control of domain-wall motion in antiferromagnetic compounds.
  • Monocolor and color holography of pre-Hispanic Colombian goldwork: a way of Colombian heritage appropriation
    Item type: Conference Paper
    Madrid Sanchez, Alejandro; Giraldo Castaño, Leidy Marcela; Velasquez Prieto, Daniel (2018)
    Proceedings of SPIE ~ Practical Holography XXXII: Displays, Materials, and Applications
  • Magnetoelectric Force Microscopy on Antiferromagnetic 180∘ Domains in Cr₂O₃
    Item type: Journal Article
    Schoenherr, Peggy; Giraldo Castaño, Leidy Marcela; Lilienblum, Martin; et al. (2017)
    Materials
    Magnetoelectric force microscopy (MeFM) is characterized as methodical tool for the investigation of antiferromagnetic domain states, in particular of the 180 variety. As reference compound for this investigation we use Cr2O3. Access to the antiferromagnetic order is provided by the linear magnetoelectric effect. We resolve the opposite antiferromagnetic 180 domain states of Cr2O3 and estimate the sensitivity of the MeFM approach, its inherent advantages in comparison to alternative techniques and its general feasibility for probing antiferromagnetic order.
  • Probing domains and topological defects in ferroics
    Item type: Doctoral Thesis
    Giraldo Castaño, Leidy Marcela (2023)
    The physical and chemical functionality of solids is defined, in many aspects, by spatial inhomogeneity, with prominent examples in doped semiconductors or magnetic data storage. In materials with ferroic order, inhomogeneity manifests in the form of domains, that is, regions with different electric, magnetic, or structural long-range order separated by boundaries called domain walls. Magnetoelectric multiferroics are a particularly promising class of ordered materials because of their coexisting electric and magnetic orders rendering them candidates for low-energy or multi-state storage devices. In particular, the interplay between electric and magnetic order within domains and at domain walls endows magnetoelectric multiferroics with unique functional degrees of freedom. However, our understanding of these phenomena still resides at a fundamental level. This doctoral thesis unveils the electric and magnetic interplay on the domain level at the microscopic scale and discusses a control route to tailor the average domain size on a sub-micron length scale. In addition, novel methodologies to probe domain populations below the optical resolution limit are explored. As a model compound, hexagonal manganites are investigated. In these compounds, electric and magnetic orders arise independently, and therefore the interplay between the orders is expected to be weak or non-mandatory. This is in contrast to multiferroic materials where the electric order is directly induced by the magnetic order, and the interplay is therefore inherently pronounced, leading to one-to-one rigidly coupled magnetoelectric domains. Importantly, however, the independence of electric and magnetic orders in the hexagonal manganites can leave the freedom for a richer landscape of domains and domain walls. It is shown in this doctoral thesis that hexagonal manganites indeed show a rich variety of domain walls. More specifically, three types of magnetic(-electric) domain walls are identified, along with magnetic vortices that form between the different domain wall intersections. This rich landscape of domain walls and vortices has its origins --- contrary to general belief --- in a pronounced bulk magnetoelectric coupling phenomenon present in these materials. Moving forward, another inherent aspect that determines the functionality of ordered materials is the average domain size which, in principle, defines how small an information ``bit'' can be made. This doctoral thesis explores chemical substitution as a route to tailor the domain size in hexagonal manganites from the micron- down to the angstrom range while preserving the inherent bulk magnetoelectric coupling mechanism. The investigation of domains in the sub-micrometer range requires imaging techniques that overcome the limitations of optical resolution. To circumvent this limitation, an experimental proof-of-concept is presented. More specifically, by combining pixel-by-pixel analysis and numerical simulations, we expand the capabilities of far-field optical second-harmonic generation (SHG) to probe nanodomain populations. In addition, combined SHG and scanning probe techniques (SPM) enable studies on the level of individual domain walls. The research results presented in this doctoral thesis, hence, provide insights that expand the field of multiferroics from a fundamental but also from a methodical point of view. These findings are relevant not only for bulk multiferroic systems but could be extended to the emergent field of thin-film multiferroics, for example to explore magnetoelectric coupling effects in hexagonal manganites thin films or to tailor magnetoelectric domains during synthesis. These results highlight the importance of microscopic inhomogeneity, specifically domains and domain walls, and its potential to promote their magnetoelectric functionality in these materials.
  • Magnetoelectric domain engineering from micrometer to Ångstrøm scales
    Item type: Journal Article
    Giraldo Castaño, Leidy Marcela; Simonov, Arkadiy; Sim, Hasung; et al. (2024)
    Physical Review Research
    The functionality of magnetoelectric multiferroics depends on the formation, size, and coupling of their magnetic and electric domains. Knowing the parameters guiding these criteria is a key effort in the emerging field of magnetoelectric domain engineering. Here we show, using a combination of piezoresponse-force microscopy, nonlinear optics, and x-ray scattering, that the correlation length setting the size of the ferroelectric domains in the multiferroic hexagonal manganites can be engineered from the micron range down to a few unit cells under the substitution of Mn3+ ions with Al3+ ions. The magnetoelectric coupling mechanism between the antiferromagnetic Mn3+ order and the distortive-ferroelectric order remains intact even at substantial replacement of Mn3+ by Al3+. Hence, chemical substitution proves to be an effective tool for domain-size engineering in one of the most studied classes of multiferroics.
  • Magnetoelectric coupling of domains, domain walls and vortices in a multiferroic with independent magnetic and electric order
    Item type: Journal Article
    Giraldo Castaño, Leidy Marcela; Meier, Quintin N.; Bortis, Amadé; et al. (2021)
    Nature Communications
    Magnetically induced ferroelectrics exhibit rigidly coupled magnetic and electric order. The ordering temperatures and spontaneous polarization of these multiferroics are notoriously low, however. Both properties can be much larger if magnetic and ferroelectric order occur independently, but the cost of this independence is that pronounced magnetoelectric interaction is no longer obvious. Using spatially resolved images of domains and density-functional theory, we show that in multiferroics with separately emerging magnetic and ferroelectric order, the microscopic magnetoelectric coupling can be intrinsically strong even though the macroscopic leading-order magnetoelectric effect is forbidden by symmetry. We show, taking hexagonal ErMnO3 as an example, that a strong bulk coupling between the ferroelectric and antiferromagnetic order is realized because the structural distortions that lead to the ferroelectric polarization also break the balance of the competing superexchange contributions. We observe the manifestation of this coupling in uncommon types of topological defects like magnetoelectric domain walls and vortex-like singularities.
Publications 1 - 6 of 6