Julie Karel
Max Planck Society
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Featured researches published by Julie Karel.
Science Advances | 2016
Ajaya K. Nayak; Julia Fischer; Yan Sun; Binghai Yan; Julie Karel; A. C. Komarek; Chandra Shekhar; Nitesh Kumar; Walter Schnelle; J. Kübler; Claudia Felser; Stuart S. P. Parkin
A large anomalous Hall effect is observed in the triangular antiferromagnet Mn3Ge arising from an intrinsic electronic Berry phase. It is well established that the anomalous Hall effect displayed by a ferromagnet scales with its magnetization. Therefore, an antiferromagnet that has no net magnetization should exhibit no anomalous Hall effect. We show that the noncolinear triangular antiferromagnet Mn3Ge exhibits a large anomalous Hall effect comparable to that of ferromagnetic metals; the magnitude of the anomalous conductivity is ~500 (ohm·cm)−1 at 2 K and ~50 (ohm·cm)−1 at room temperature. The angular dependence of the anomalous Hall effect measurements confirms that the small residual in-plane magnetic moment has no role in the observed effect except to control the chirality of the spin triangular structure. Our theoretical calculations demonstrate that the large anomalous Hall effect in Mn3Ge originates from a nonvanishing Berry curvature that arises from the chiral spin structure, and that also results in a large spin Hall effect of 1100 (ħ/e) (ohm·cm)−1, comparable to that of platinum. The present results pave the way toward the realization of room temperature antiferromagnetic spintronics and spin Hall effect–based data storage devices.
ACS Nano | 2014
Julie Karel; Carlos E. ViolBarbosa; Janos Kiss; Jaewoo Jeong; Nagaphani Aetukuri; Mahesh G. Samant; Xeniya Kozina; Eiji Ikenaga; Gerhard H. Fecher; Claudia Felser; Stuart S. P. Parkin
The development of new phases of matter at oxide interfaces and surfaces by extrinsic electric fields is of considerable significance both scientifically and technologically. Vanadium dioxide (VO2), a strongly correlated material, exhibits a temperature-driven metal-to-insulator transition, which is accompanied by a structural transformation from rutile (high-temperature metallic phase) to monoclinic (low-temperature insulator phase). Recently, it was discovered that a low-temperature conducting state emerges in VO2 thin films upon gating with a liquid electrolyte. Using photoemission spectroscopy measurements of the core and valence band states of electrolyte-gated VO2 thin films, we show that electronic features in the gate-induced conducting phase are distinct from those of the temperature-induced rutile metallic phase. Moreover, polarization-dependent measurements reveal that the V 3d orbital ordering, which is characteristic of the monoclinic insulating phase, is partially preserved in the gate-induced metallic phase, whereas the thermally induced metallic phase displays no such orbital ordering. Angle-dependent measurements show that the electronic structure of the gate-induced metallic phase persists to a depth of at least ∼40 Å, the escape depth of the high-energy photoexcited electrons used here. The distinct electronic structures of the gate-induced and thermally induced metallic phases in VO2 thin films reflect the distinct mechanisms by which these states originate. The electronic characteristics of the gate-induced metallic state are consistent with the formation of oxygen vacancies from electrolyte gating.
Journal of Physics D | 2015
Olga Meshcheriakova; Albrecht Köhler; Siham Ouardi; Yukio Kondo; Takahide Kubota; Shekhar Chandra; Julie Karel; Carlos Viol Barbosa; Rolf Stinshoff; Roshnee Sahoo; Shigenori Ueda; Eiji Ikenaga; Shigemi Mizukami; Stanislav Chadov; Daniel Ebke; Gerhard H. Fecher; Claudia Felser
Epitaxial thin films of Mn2RhSn were grown on a MgO(0 0 1) substrate by magnetron co-sputtering of the constituents. An optimised range of temperature for heat treatment was used to stabilise the tetragonal structure and to prevent the capping Rh layer from diffusing into the Heusler layer. Electronic and magnetic properties were analysed by hard x-ray photoelectron spectroscopy as well as field- and temperature-dependent Hall and resistivity measurements. The measured valence spectra are in good agreement with the calculated density of states. The measured saturation magnetisation corresponds to a magnetic moment of 1 μB in the primitive cell. The magnetisation measurements revealed an out-of-plane anisotropy energy of 89 kJ m−3 and a maximum energy product of 3.3 kJ m−3. The magnetoresistance ratio is 2% for fields of 9 T. The lattice parameter of the compound has a very small mismatch with MgO, which makes it promising for coherent electron tunnelling phenomena.
Journal of Non-crystalline Solids | 2015
D. R. Queen; Xiao Liu; Julie Karel; H.C. Jacks; Thomas Metcalf; F. Hellman
In
New Journal of Physics | 2016
K G Rana; O Meshcheriakova; J Kübler; B Ernst; Julie Karel; R Hillebrand; Eckhard Pippel; P. Werner; Ajaya K. Nayak; Claudia Felser; Stuart S. P. Parkin
e
Proceedings of the National Academy of Sciences of the United States of America | 2016
Carlos E. ViolBarbosa; Julie Karel; Janos Kiss; Ovidiu-dorin Gordan; Simone G. Altendorf; Yukumi Utsumi; Mahesh G. Samant; Yu-Han Wu; Ku-Ding Tsuei; Claudia Felser; Stuart S. P. Parkin
-beam evaporated amorphous silicon (
Nano Research | 2017
Changhai Wang; Aleksandr A. Levin; Julie Karel; Simone Fabbrici; Jinfeng Qian; Carlos E. ViolBarbosa; Siham Ouardi; F. Albertini; Walter Schnelle; Jan Rohlicek; Gerhard H. Fecher; Claudia Felser
a
Materials Research Express | 2014
Julie Karel; Y N Zhang; Catherine Bordel; Kevin H. Stone; T. Y. Chen; C. A. Jenkins; David J. Smith; J Hu; Ruqian Wu; S M Heald; J. B. Kortright; F. Hellman
-Si), the densities of two-level systems (TLS),
Journal of Materials Chemistry C | 2017
Julie Karel; Julia Fischer; Simone Fabbrici; E. Pippel; P. Werner; M. Vinicius Castergnaro; Peter Adler; Siham Ouardi; B. Balke; Gerhard H. Fecher; J. Morais; F. Albertini; Stuart S. P. Parkin; Claudia Felser
n_{0}
Applied Physics Letters | 2017
Julie Karel; F. Casoli; L. Nasi; P. Lupo; Roshnee Sahoo; Benedikt Ernst; Anastasios Markou; Adel Kalache; R. Cabassi; F. Albertini; Claudia Felser
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