Magnetic nanoparticles; Photoemission electron microscopy; X-rays
Jal Emmanuelle, Makita Mikako, Rösner Benedikt, David Christian, Nolting Frithjof, Raabe Jörg, Savchenko Tatiana, Kleibert Armin, Capotondi Flavio, Pedersoli Emanuele, Raimondi Lorenzo, Manfredda Michele, Nikolov Ivaylo, Liu Xuan, Merhe Alaa el dine, Jaouen Nicolas, Gorchon Jon, Malinowski Gregory, Hehn Michel, Vodungbo Boris, Lüning Jan (2019), Single-shot time-resolved magnetic x-ray absorption at a free-electron laser, in Physical Review B
, 99(14), 144305-144305.
Luo Zhaochu, Dao Trong Phuong, Hrabec Aleš, Vijayakumar Jaianth, Kleibert Armin, Baumgartner Manuel, Kirk Eugenie, Cui Jizhai, Savchenko Tatiana, Krishnaswamy Gunasheel, Heyderman Laura J., Gambardella Pietro (2019), Chirally coupled nanomagnets, in Science
, 363(6434), 1435-1439.
Vijayakumar Jaianth, Bracher David, Savchenko Tatiana M., Horisberger Michael, Nolting Frithjof, Vaz C. A. F. (2019), Electric field control of magnetism in Si 3 N 4 gated Pt/Co/Pt heterostructures, in Journal of Applied Physics
, 125(11), 114101-114101.
Baldrati L., Ross A., Niizeki T., Schneider C., Ramos R., Cramer J., Gomonay O., Filianina M., Savchenko T., Heinze D., Kleibert A., Saitoh E., Sinova J., Kläui M. (2018), Full angular dependence of the spin Hall and ordinary magnetoresistance in epitaxial antiferromagnetic NiO(001)/Pt thin films, in Physical Review B
, 98(2), 024422-024422.
Magnetic nanoparticles offer to study a rich variety of complex interactions, leading to new insights into fundamental physical properties and enabling to design functionalities in advanced materials. They are relevant in magnetic data storage application and are employed in sensors and medical applications. Understanding the scaling laws covering their properties and resolving the competing energy contributions is important in order to advance this field. Unique phenomena of magnetic nanoparticles are stable single domain states and superparamagnetic behaviour. Despite of considerable experimental and theoretical efforts, a clear understanding of their size-dependent properties has not yet been achieved. This is largely due to a distinct sensitivity of the nanoparticles magnetic properties to their microscopic structure and the details of their interfacial coupling. Here, we propose to tackle this challenge with a novel experimental approach to study the properties of individual magnetic nanoparticles. We will further push the limits of X-ray photoemission electron microscopy for the detection of single nanoparticles taking full advantage of the elemental, chemical, magnetic and electronic sensitivity of spatially resolved X-ray absorption spectroscopy. In this project, we will focus onto single pure and multi-component nanoparticles of 3d transition metals in the size range of 5-25 nm and will address the following two main questions:•What is the interplay of structure, surface and magnetic properties of nanoparticles?•Can this interplay be used to push the all-optical manipulation of magnetism down to nanoparticles?In particular, we will study the effect of external stimuli such as chemical dosing and ultra-short laser pulses onto the static and dynamic magnetic properties of the nanoparticles. The latter is an intriguing new pathway for an alternative “non-magnetic” approach to control spin systems, since it has been discovered that ultrafast laser pulses can reverse the magnetization in certain magnetic materials. The underlying physical mechanism is subject to intense experimental and theoretical research. However, most of these efforts focus so far on extended thin film systems. Within this project we aim to study optical manipulation in magnetic nanoparticles. Besides their particular relevance for applications, we expect that making use of their unique properties will contribute to the understanding of all-optical control in magnetic materials. Another important emphasis is to correlate the microscopic structure with the magnetic properties by measuring the very same, isolated individual nanoparticles with X-ray photoemission electron microscopy and with high resolution transmission electron microscopy. This unique capability will enable to achieve a fundamental understanding of nanoparticle magnetism as well as to provide canonical datasets, which can serve as testing ground for theory.