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Magnetic materials at the nanoscale: Low-Energy Electron Microscopy as an analytical tool

AuthorsPrieto, José E.
Issue Date11-Apr-2019
CitationHumboldt Colloquium (2019)
AbstractMagnetic materials are essential in our everyday life in applications ranging from information storage and processing to devices for efficient production and use of energy. Many of these make use of magnetic systems of nanometric sizes, as the exchange-coupled magnetic thin films of modern magnetoresistive reading heads or the recently proposed race-track memories, in which information is read by the motion of magnetic domains due to spin-polarized currents. Generally, in >spintronic> devices, one aims at controlling the spin degree of freedom of electrons in order to achieve significantly higher access speeds and computation efficiencies. Appart from the obvious technological interest, many basic-science questions related to dimensionality reduction remain open. In our projects, we aim at the fabrication and characterization of thin films and nanostructures of magnetic materials based on transition metal oxides. These offer a wide range of functionalities since their magnetic properties can be taylored by controlling composition, size and shape, atomic structure or film morphology. We employ vacuum-based methods for the synthesis of epitaxial materials and characterize them both by in-situ and ex-situ analytical techniques. In particular, we are currently studying the growth of mixed Fe-Co and Fe-Ni oxides where a control of the composition allows the tayloring of the surface morphology and of the magnetic properties of the mixed fims, like the Néel temperature of the antiferromagnetic compounds or the magnetic hardness of the ferromagnetic materials. Another class of materials we plan to explore are oxides of rare earths due to the increased anisotropy they produce and which makes them extremely important for the fabrication of hard magnetic materials. However, control of properties at the nanoscale remains a challenge due to the critical influence of structural defects that proliferate at the ultrathin level (surface roughness, presence of antiphase boundaries, etc.) Therefore, the study of spintronic materials requires advanced experimental techniques. In addition to more conventional ones, we are increasingly making use of low-energy electron microscopy and photoemission microscopies (LEEM-PEEM). These techniques present many useful characteristics but the most relevant for our purposes are their high surface sensitivity, the possibility of performing dynamical studies (e.g. real-time monitoring of crystal growth) and the possibility of obtaining magnetic contrast e.g. by the use of polarized synchrotron radiation, which allows the determination of magnetic domain structures.
DescriptionHumboldt Colloquium: “Research without Borders – Alexander von Humboldt’s Legacy Today”, Madrid, Spain, 11 – 13 April 2019
Appears in Collections:(IQFR) Comunicaciones congresos
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