Carolin Schmitz-Antoniak

Carolin Schmitz-Antoniak
Technische Hochschule Wildau | TH Wildau · Fachbereich Ingenieur und Naturwissenschaften

Professor

About

66
Publications
16,413
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,229
Citations
Additional affiliations
February 2014 - June 2021
Forschungszentrum Jülich
Position
  • Group Leader
Education
January 2008 - December 2013
University of Duisburg-Essen
Field of study
  • Experimental physics
May 2004 - December 2007
University of Duisburg-Essen
Field of study
  • Physics
October 1999 - April 2004

Publications

Publications (66)
Article
Full-text available
Magnetic nanoparticles are of immense current interest because of their possible use in biomedical and technological applications. Here we demonstrate that the large magnetic anisotropy of FePt nanoparticles can be significantly modified by surface design. We employ X-ray absorption spectroscopy offering an element-specific approach to magnetocryst...
Article
Full-text available
Ferrimagnetic CoFe2O4 nanopillars embedded in a ferroelectric BaTiO3 matrix are an example for a two-phase magnetoelectrically coupled system. They operate at room temperature and are free of any resource-critical rare-earth element, which makes them interesting for potential applications. Prior studies succeeded in showing strain-mediated coupling...
Article
Full-text available
The intra-atomic magnetic dipole moment - frequently called 〈Tz〉 term - plays an important role in the determination of spin magnetic moments by x-ray absorption spectroscopy for systems with nonspherical spin density distributions. In this work, we present the dipole moment as a sensitive monitor to changes in the electronic structure in the vicin...
Article
Full-text available
X-ray absorption spectroscopy facilitated by state-of-the-art synchrotron radiation technology is presented as a powerful tool to study nanoscale systems, in particular revealing their static element-specific magnetic and electronic properties on a microscopic level. A survey is given on the properties of nanoparticles, nanocomposites and thin film...
Article
Full-text available
The case of palladium(II) ions in molecular polyoxopalladates highlights the importance of accounting not only for nearest neighbour atoms or ions in order to understand, model or predict magnetic characteristics. Here, using site-specific soft X-ray magnetic circular dichroism (XMCD), the effects of different bond lengths, delocalization of 4d ele...
Article
Time-dependent and constituent-specific spectral changes in soft near-edge x-ray absorption spectroscopy (XAS) of an [Fe/MgO]8 metal/insulator heterostructure after laser excitation are analyzed at the O K-edge with picosecond time resolution. The oxygen absorption edge of the insulator features a uniform intensity decrease of the fine structure at...
Article
Nuclear resonant reflectivity (NRR) from an Fe 60 Al 40 film was measured using synchrotron radiation at several grazing angles near the critical angle of total external reflection. Using laterally resolved measurements after irradiation with 20 keV Ne ⁺ ions of gradually varying fluence of 0–3.0 × 10 ¹⁴ ions cm ⁻² , the progressive creation of the...
Article
Full-text available
Decoration with Pd clusters increases the magnetic heating ability of cobalt ferrite (CFO) nanoparticles by a factor of two. The origin of this previous finding is unraveled by element-specific X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) combined with atomic multiplet simulations and density functional theory (DFT) ca...
Article
A new polyoxometalate compound consisting of the 39-tungsto-4-arsenate(III) unit with four incorporated VIV ions, isolated as (NH4)22[(VIVO)2(VIVO(H2O))(AsIIIWVI9O33)2(AsIIIWVI8.5VIV0.5(OH)O32)2(WVIO2)4]·48H2O (NH 4 -As 4 W 39 (V 4 )), was synthesized and fully characterized. SQUID magnetometry shows three weakly coupled VIV centers with an antifer...
Article
Loss mechanisms in fluid heating of cobalt ferrite (CFO) nanoparticles and CFO–Pd heterodimer colloidal suspensions are investigated as a function of particle size, fluid concentration and magnetic field amplitude. The specific absorption rate (SAR) is found to vary with increasing particle size due to a change in dominant heating mechanism from su...
Article
Polyoxopalladates hosting 3d, 4d or 4f central ions form a new class of molecular materials with well-defined, tunable morphology and ions coordination to be considered as model systems for basic research. We investigated the isotropic x-ray absorption near-edge structure (XANES), x-ray magnetic circular dichroism (XMCD), and x-ray magnetic linear...
Preprint
Time-dependent and constituent-specific spectral changes in transient soft x-ray spectroscopy of an [Fe/MgO]$_8$ metal/insulator heterostructure upon laser excitation are analyzed at the Fe L$_3$-edge and the O K-edge with picosecond and femtosecond time resolution. While the transition metal edge exhibits an energy red-shift of the spectra for ele...
Article
The element specificity of soft x-ray spectroscopy makes it an ideal tool for analyzing the microscopic origin of ultrafast dynamics induced by localized optical excitation in metal-insulator heterostructures. Using [Fe/MgO]n as a model system, we perform ultraviolet pump/soft x-ray probe experiments, which are sensitive to all constituents of thes...
Article
V2O3 doped with 1.1% Cr is investigated at its isostructural correlation‐driven metal‐insulator transition near room temperature in its paramagnetic state with X‐ray magnetic circular dichroism (XMCD) spectroscopy in external magnetic fields. A relative XMCD amplitude of about two permille is observed at the L2,3 absorption edges of vanadium as exp...
Article
Full-text available
In this contribution, we analyze the properties of two-phase magneto-electric (ME) composites. Such ME composite materials have raised scientific attention in the last decades due to many possible applications in a wide range of technical devices. Since the effective magneto-electric properties significantly depend on the microscopic morphology, we...
Preprint
Exploiting the element specificity of soft x-ray spectroscopy, we analyze the microscopic origin of ultrafast non-local dynamics induced by localized optical excitation in metal-insulator heterostructures. The performed ultraviolet pump - soft x-ray probe experiment is sensitive to all constituents of the [Fe/MgO]$_n$ heterostructures, and probes e...
Article
We demonstrate the emergence and control of magnetic phases between magnetite (Fe3O4), a ferrimagnetic halfmetal, and SrTiO3, a transparent non-magnetic insulator considered the bedrock of oxide-based electronics. The Verwey transition (TV) was detected to persist from bulk-like down to ultrathin Fe3O4 films, decreasing from 117±4 K (38 nm) to 25±4...
Article
Full-text available
Magnetic-plasmonic heterodimer nanostructures synergistically present excellent magnetic and plasmonic characteristics in a unique platform as a multipurpose medium for recently invented biomedical applications, such as magnetic hyperthermia, photothermal therapy, drug delivery, bioimaging, and biosensing. In this review, we briefly outline the les...
Article
Full-text available
Dodecapalladium(II) oxide‐based molecular nanocubes encapsulating Fe3+ (3d5) or Co2+ (3d7) ions display facile hydrogen uptake with concurrent pronounced magnetization changes that suggests use as molecular hydrogen detection materials. Electronic and magnetic properties were investigated element‐specifically by X‐ray absorption spectroscopy and it...
Article
A series of unprecedented supramolecular associates of phenylarsonate‐capped {MIIPdII12O8}‐type (M = Co, Ni and Zn) polyoxopalladates with α‐cyclodextrins (α‐CD) was obtained and characterized in the solid state (single‐crystal X‐ray diffraction (XRD), FT‐IR spectroscopy, elemental and thermogravimetric (TGA) analyses), in aqueous solution (1H and...
Article
Hard x-ray absorption and magnetic circular dichroism spectroscopy have been applied to study the consequential changes of the local environment around Fe atoms and their orbital polarizations in 40 nm thick Fe60Al40 thin films along the order-disorder (B2→A2) phase transition initiated by 20-keV Ne+ ion irradiation with fluences of (0.75–6)×1014io...
Article
Charge Trapping The Verwey phase transition in magnetite core nanoparticles with an amorphous shell is investigated by Carolin Schmitz‐Antoniak and co‐workers in article number 1700363. Ions with localized electrons trapped at interfacial defects at the surface can suppress the Verwey transition. Synchrotron radiation spectroscopy in conjunction wi...
Article
Full-text available
The Verwey transition in Fe3O4 nanoparticles with a mean diameter of 6.3 nm is suppressed after capping the particles with a 3.5 nm thick shell of SiO2. By X-ray absorption spectroscopy and its associated X-ray magnetic circular dichroism this suppression can be correlated to localized Fe²⁺ states and a reduced double exchange visible in different...
Article
Structural properties of cobalt ferrite nanoparticles have significant effects on its magnetic behavior. In current study, we thoroughly scrutinized and optimized the structural characteristics of CoFe2O4 nanoparticles and the correlation with its magnetic properties as a function of the synthesis parameters using Rietveld structure refinement. Nan...
Article
We create an interface of graphene with a metallic and magnetic support that leaves its electronic structure largely intact. This is achieved by exposing epitaxial graphene on ferromagnetic thin films of Co and Ni to vapor of the rare earth metal Eu at elevated temperatures, resulting in the intercalation of an Eu monolayer in between graphene and...
Article
The performance of magnetic nanoparticles in different applications is severely depended on their size characteristics, so the study of effective parameters on these properties can play significant roles in qualifications of nanoparticles. In present work, some important factors on size features of CoFe2O4 superparamagnetic nanoparticles include th...
Article
Full-text available
Magnetite (Fe3O4) nanoparticles suffer from severe ageing effects when exposed to air even when they are dispersed in a solvent limiting their applications. In this work, we show that this ageing can be fully reversed by a hydrogen plasma treatment. By x-ray absorption spectroscopy and its associated magnetic circular dichroism, the electronic stru...
Article
In this article we report on the synthesis and multiferroic properties of cobalt ferrite (CoFe2O4)–barium titanate (BaTiO3) biphasic composites. The initial composite nanopowder was synthesized by a combination of co-precipitation and organosol methods. A ceramic sample with (3–0) connectivity, i.e. BaTiO3 grains in a CoFe2O4 matrix was obtained by...
Article
Magnetoelectric coupling is the material based coupling between electric and magnetic fields without recurrence to electrodynamics. It can arise in intrinsic multiferroics as well as in composites. Intrinsic multiferroics rely on atomistic coupling mechanisms, or coupled crystallographic order parameters, and even more complex mechanisms. They typi...
Article
Full-text available
Novel methods of switching magnetism with electric fields and vice versa, and aiming at magnetoelectric (ME) data processing are reported. First, the patented MERAM @ uses the electric field control of exchange bias via an epitaxial Cr 2 O 3 layer and exchange coupling to a Pt/Co/Pt trilayer. It promises to crucially reduce Joule energy losses in R...
Article
The coupling of submonolayer coverages of Fe-phthalocyanine molecules on bare and oxygen-covered ferromagnetic Co(001) films was studied by x-ray-absorption spectroscopy, especially the x-ray magnetic circular dichroism, in combination with density functional theory. We observe that the magnetic moments of the paramagnetic molecules are aligned eve...
Article
Full-text available
Abrupt room temperature switching (Tc = 295 K with a 5 K hysteresis) was achieved in a neutral Fe(II) complex based on a 2-(1H-pyrazol-1-yl)-6-(1H-tetrazol-5-yl)pyridine ligand. Structural characterization and spin crossover study (via SQUID magnetometry, photoexcitation and X-ray absorption spectroscopy) in the solid state are described.
Article
The influence of local chemical composition, structure and surface modifications on the magnetic properties of FexPt1 − x nanoparticles around the equiatomic composition have been studied by means of X-ray absorption spectroscopy (XAS). In particular, the extended X-ray absorption fine structure (EXAFS) and the X-ray magnetic circular dichroism (XM...
Article
The effectiveness of amine-borane as reducing agent for the synthesis of iron nanoparticles has been investigated. Large (2-4 nm) Fe nanoparticles were obtained from [Fe{N(SiMe3 )2 }2 ]. Inclusion of boron in the nanoparticles is clearly evidenced by extended X-ray absorption fine structure spectroscopy and Mössbauer spectrometry. Furthermore, the...
Article
The structural and magnetic properties of Fe octaethylporphyrin (OEP) molecules on Cu(001) have been investigated by means of density functional theory (DFT) methods and X-ray absorption spectroscopy. The molecules have been adsorbed on the bare metal surface and on an oxygen-covered surface, which shows a $\sqrt{2}\times2\sqrt{2}R45^{\circ}$ recon...
Article
Using size-selected spherical FePt nanoparticles and cubic Fe/Fe-oxide nanoparticles as examples, we discuss the recent progress in the determination of static and dynamic properties of nanomagnets. Synchroton radiation-based characterisation techniques in combination with detailed structural, chemical and morphological investigations by transmissi...
Article
Full-text available
Fe3O4 nanoparticles have been investigated as they are biocompatible and their surface can be functionalized. We synthesized iron oxide nanoparticles using a water-in-oil microemulsion method. Bare and silica-coated iron oxide nanoparticles of a core size of 6 nm dispersed in ethanol have been investigated by means of x-ray absorption spectroscopy...
Article
Full-text available
Element-specific magnetic moments of epitaxially grown Fe3Si in D03 crystal symmetry were analyzed by means of x-ray absorption spectroscopy and its associated magnetic circular dichroism. To detect the weak magnetization induced at the Si sites, measurements were performed at both the Si K edge and the Si L3,2 edges. By band structure calculations...
Article
Full-text available
The disorder–order transition of a highly defective A2-ordered Cu2MnAl film on MgO(0 0 1) upon annealing at 600 K was monitored by means of x-ray absorption spectroscopy (XAS) at the Cu and Mn L2,3 edges. Additionally, x-ray magnetic circular dichroism (XMCD) was employed to determine element-specific orbital and spin resolved magnetic moments of t...
Article
By magnetic coupling of Fe and Gd via Cr interlayers, the large local moment of Gd can be combined with the high Curie temperature of Fe. The textured growth of a Gd film is studied here by preparing trilayer systems of Fe/Cr/Gd on MgO(1 0 0) substrates by molecular-beam epitaxy (MBE). The thickness of the Cr interlayer was varied between 3 and 5 m...
Article
Full-text available
Electronic and magnetic properties strongly depend on the structure of the material, especially on the crystal symmetry and chemical environment. In nanoparticles, the break of symmetry at the surface may yield different physical properties with respect to the corresponding bulk material. A useful tool to investigate the electronic structure, magne...
Article
We investigate the influence of lattice distortion and off-stoichiometry on the electronic and magnetic properties of Co2+x Fe1−xSi Heusler alloys in their L21 bulk phase and on MgO(001) using the density functional theory. Our investigations show that Co excess does not significantly change the magnetic properties, whereas an increase of the Fe co...
Article
Full-text available
X-ray absorption spectroscopy methods are presented as a useful tool to determine local structure, composition and magnetic moments as well as to estimate the effective anisotropy of substrate supported self-assembled arrays of wet-chemically synthesized FePt nanoparticles. A compositional inhomogeneity within the nanoparticles yields reduced magne...
Article
Full-text available
The exchange stiffness constants of chemically disordered FexPt1-x films with thickness around 50 nm were determined by means of ferromagnetic resonance. It was found to increase with increasing Fe content from 6±4pJ/m for x=0.27 to 15±4pJ/m for x=0.67 . Theoretical results from fully relativistic and scalar-relativistic band-structure calculations...
Article
Full-text available
Using density functional calculations, we have studied the magnetic properties of nanocomposites composed of rare-earth-metal elements in contact with 3d transition metals (Fe and Cr). We demonstrate the possibility to obtain huge magnetic moments in such nanocomposites, of order 10mu(B)/rare-earth-metal atom, with a potential to reach the maximum...
Chapter
An introduction is given to the X-ray magnetic dichroism focussing on X-ray magnetic circular dichroism (XMCD). The standard analysis of XMCD spectra by using the sum rules is elucidated. Additionally, aspects of the experimental realization and the data analysis are presented. By means of experimental examples of light 3d metal films, rare earth s...
Article
Full-text available
For a detailed understanding of the interface between Fe3Si and GaAs, we investigate Fe3Si films in the ultrathin limit down to a few monolayers and compare the results to Fe3Si/MgO(001) which serves as a reference in the present study. From X-ray magnetic circular dichroism measurements we determine averaged spin and orbital magnetic Fe moments. F...
Article
Full-text available
The influence of structural and compositional changes within FePt nanoparticles on their magnetic properties was studied by means of x-ray absorption spectroscopy in the near-edge regime and its associated magnetic circular dichroism as well as by analysis of the extended x-ray absorption fine structure. The magnetic moments at the Fe sites were fo...
Article
Full-text available
We investigated the magnetic as well as the structural properties of Fe3Si films on GaAs(001)-(4×6), GaAs(001)-(2×2), and MgO(001) by x-ray magnetic circular dichroism (XMCD) and Mössbauer spectroscopy. From the XMCD spectra we determine averaged magnetic moments of 1.3–1.6μB per Fe atom on the different substrates by a standard sum-rule analysis....
Article
Full-text available
The reduced magnetic moments of oxide-free FePt nanoparticles are discussed in terms of lattice expansion and local deviation from the averaged composition. By analyses of the extended x-ray absorption fine structure of FePt nanoparticles and bulk material measured both at the Fe K and Pt L(3) absorption edge, the composition within the single nano...
Article
Full-text available
We study the diffusion of 57 Fe probe atoms in Fe/FeSi/Si/FeSi/Fe multilayers on Si(111) prepared by molecular beam epitaxy by means of 57 Fe conversion electron Mössbauer spectroscopy (CEMS). We demonstrate that the application of FeSi boundary layers successfully inhibits the diffusion of 57 Fe into the Si layer. The critical thickness for the co...
Article
Full-text available
Wet-chemically synthesized FePt nanoparticles were structurally characterized not only in the as-prepared state but also after the removal of organic ligands and reduction in Fe oxides by a soft in situ hydrogen plasma treatment. By the analyses of the extended x-ray absorption fine structures at the Pt L3 absorption edge, we found an enhanced latt...
Article
Full-text available
FexPt1-x nanoparticles prepared by organometallic synthesis and gas-phase condensation were structurally and magnetically characterised. The effective spin magnetic moments at both the Fe and Pt sites are reduced with respect to the moments in the corresponding bulk material by up to 20% and further decrease with decreasing particle size at the Fe...
Article
Full-text available
We present results of x-ray absorption spectroscopy and x-ray magnetic circular dichroism investigations at the L-3,L-2 edges of Fe in FePt nanoparticles. Plasma treated, oxide-free FePt nanoparticles with a high degree of L1(0) ordering and a mean diameter of about 6 nm were produced by gas phase condensation followed by in situ flight annealing....
Article
Full-text available
FePt particles 6 nm in size are produced by argon/nitrogen sputtering and gas-phase condensation. Marked changes in the atomic structure and morphology of the particles occur upon addition of nitrogen to the sputter gas. Electron energy loss spectroscopy and x-ray absorption spectroscopy show that nitrogen is incorporated in the particles in molecu...
Article
Full-text available
X-ray absorption and magnetic circular dichroism spectra at both the Fe and Pt L-3,L-2 edges were measured on wet-chemically synthesized monodisperse Fe50Pt50 particles with a mean diameter of 6.3 nm before and after complete removal of the organic ligands and the oxide shell covering the particles by soft hydrogen plasma resulting in a pure metall...
Article
Multifrequency ferromagnetic resonance well above the blocking temperature was used to determine the composition dependent g-factor in wet-chemically synthesized FexPt1-x nanoparticles with mean diameters around 3 nm. The magnetic relaxation process in these experiments is found to be non-Gilbert like. To obtain the blocking temperature and the eff...
Article
Full-text available
Ferromagnetic resonance measurements probe the dynamical response of magnetic systems due to an excitation within the microwave regime. Offering high sensitivity and energy resolution in the μeV range of ferromagnetic resonance this technique is well suited for the investigation of magnetic anisotropy in nanoscale systems. Ferromagnetic Resonance e...
Article
Full-text available
The effective magnetic anisotropy Keff of chemically disordered Fe70Pt30 particles with a mean diameter of 2.3 nm is shown to be temperature dependent between 50 K and 350 K. From the determination of the blocking temperatures by field-cooled and zero-field-cooled magnetisation measurements and ferromagnetic resonance experiments, that is in two di...