TY  - JOUR
A1  - Vogel, Patrick
A1  - Rückert, Martin Andreas
A1  - Friedrich, Bernhard
A1  - Tietze, Rainer
A1  - Lyer, Stefan
A1  - Kampf, Thomas
A1  - Hennig, Thomas
A1  - Dölken, Lars
A1  - Alexiou, Christoph
A1  - Behr, Volker Christian
T1  - Critical Offset Magnetic PArticle SpectroScopy for rapid and highly sensitive medical point-of-care diagnostics
JF  - Nature Communications
N2  - Magnetic nanoparticles (MNPs) have been adapted for many applications, e.g., bioassays for the detection of biomarkers such as antibodies, by controlled engineering of specific surface properties. Specific measurement of such binding states is of high interest but currently limited to highly sensitive techniques such as ELISA or flow cytometry, which are relatively inflexible, difficult to handle, expensive and time-consuming. Here we report a method named COMPASS (Critical-Offset-Magnetic-Particle-SpectroScopy), which is based on a critical offset magnetic field, enabling sensitive detection to minimal changes in mobility of MNP ensembles, e.g., resulting from SARS-CoV-2 antibodies binding to the S antigen on the surface of functionalized MNPs. With a sensitivity of 0.33 fmole/50 µl (≙7 pM) for SARS-CoV-2-S1 antibodies, measured with a low-cost portable COMPASS device, the proposed technique is competitive with respect to sensitivity while providing flexibility, robustness, and a measurement time of seconds per sample. In addition, initial results with blood serum demonstrate high specificity.
KW  - biochemical assays
KW  - characterization and analytical techniques
KW  - magnetic properties and materials
KW  - nanoparticles
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-300893
VL  - 13
ER  - 
TY  - JOUR
A1  - Sessi, Paolo
A1  - Biswas, Rudro R.
A1  - Bathon, Thomas
A1  - Storz, Oliver
A1  - Wilfert, Stefan
A1  - Barla, Alessandro
A1  - Kokh, Konstantin A.
A1  - Tereshchenko, Oleg E.
A1  - Fauth, Kai
A1  - Bode, Matthias
A1  - Balatsky, Alexander V.
T1  - Dual nature of magnetic dopants and competing trends in topological insulators
JF  - Nature Communications
N2  - Topological insulators interacting with magnetic impurities have been reported to host several unconventional effects. These phenomena are described within the framework of gapping Dirac quasiparticles due to broken time-reversal symmetry. However, the overwhelming majority of studies demonstrate the presence of a finite density of states near the Dirac point even once topological insulators become magnetic. Here, we map the response of topological states to magnetic impurities at the atomic scale. We demonstrate that magnetic order and gapless states can coexist. We show how this is the result of the delicate balance between two opposite trends, that is, gap opening and emergence of a Dirac node impurity band, both induced by the magnetic dopants. Our results evidence a more intricate and rich scenario with respect to the once generally assumed, showing how different electronic and magnetic states may be generated and controlled in this fascinating class of materials.
KW  - magnetic properties and materials
KW  - topological insulators
KW  - magnetic dopants
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172704
VL  - 7
ER  - 
TY  - JOUR
A1  - Hausoel, A.
A1  - Karolak, M.
A1  - Şaşιoğlu, E.
A1  - Lichtenstein, A.
A1  - Held, K.
A1  - Katanin, A.
A1  - Toschi, A.
A1  - Sangiovanni, G.
T1  - Local magnetic moments in iron and nickel at ambient and Earth's core conditions
JF  - Nature Communications
N2  - Some Bravais lattices have a particular geometry that can slow down the motion of Bloch electrons by pre-localization due to the band-structure properties. Another known source of electronic localization in solids is the Coulomb repulsion in partially filled d or f orbitals, which leads to the formation of local magnetic moments. The combination of these two effects is usually considered of little relevance to strongly correlated materials. Here we show that it represents, instead, the underlying physical mechanism in two of the most important ferromagnets: nickel and iron. In nickel, the van Hove singularity has an unexpected impact on the magnetism. As a result, the electron–electron scattering rate is linear in temperature, in violation of the conventional Landau theory of metals. This is true even at Earth’s core pressures, at which iron is instead a good Fermi liquid. The importance of nickel in models of geomagnetism may have therefore to be reconsidered.
KW  - ferromagnetism
KW  - electronic properties and materials
KW  - magnetic properties and materials
KW  - nickel
KW  - iron
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170681
VL  - 8
IS  - 16062
ER  -