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14 results on '"Yaresko, Alexander N."'

1. Magneto-optic and transverse transport properties of non-collinear antiferromagnets

Author

Wimmer, Sebastian, Mankovsky, Sergiy, Minár, Ján, Yaresko, Alexander N., and Ebert, Hubert

Subjects
Condensed Matter - Materials Science
Abstract

Previous studies on the anomalous Hall effect in coplanar non-collinear antiferromagnets are revisited and extended to magneto-optic properties, namely magneto-optic Kerr effect (MOKE) and X-ray magnetic dichroism (XMCD). Starting from group-theoretical considerations the shape of the frequency-dependent conductivity tensor for various actual and hypothetical spin configurations in cubic and hexagonal Mn$_3X$ compounds is determined. Calculated MOKE and X-ray dichroism spectra are used to confirm these findings and to give estimates of the size of the effects. For Mn$_3$IrPt and Mn$_3$PtRh alloys the concentration dependence of the anomalous and spin Hall conductivity is studied in addition.

Published
2019
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6. Optical conductivity and superconductivity in highly overdoped La2-xCaxCuO4 thin films.

Author

Kim, Gideok, Rabinovich, Ksenia S., Boris, Alexander V., Yaresko, Alexander N., Suyolcu, Y. Eren, Yu-Mi Wu, van Aken, Peter A., Christiani, Georg, Logvenov, Gennady, and Keimer, Bernhard

Subjects
OPTICAL conductivity, THIN films, SUPERCONDUCTIVITY, MOLECULAR beam epitaxy, PHASE diagrams
Abstract

We have used atomic layer-by-layer oxide molecular beam epitaxy to grow epitaxial thin films of La2-xCaxCuO4 with x up to 0.5, greatly exceeding the solubility limit of Ca in bulk systems (x~0.12). A comparison of the optical conductivity measured by spectroscopic ellipsometry to prior predictions from dynamical mean-field theory demonstrates that the hole concentration p is approximately equal to x. We find superconductivity with Tc of 15 to 20 K up to the highest doping levels and attribute the unusual stability of superconductivity in La2-xCaxCuO4 to the nearly identical radii of La and Ca ions, which minimizes the impact of structural disorder. We conclude that careful disorder management can greatly extend the "superconducting dome" in the phase diagram of the cuprates. [ABSTRACT FROM AUTHOR]

Published
2021
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10. Revisiting Bond Breaking and Making in EuCo2P2: Where are the Electrons?

Author

Yannello, Vincent, Guillou, Francois, Yaroslavtsev, Alexander A., Tener, Zachary P., Wilhelm, Fabrice, Yaresko, Alexander N., Molodtsov, Serguei L., Scherz, Andreas, Rogalev, Andrei, and Shatruk, Michael

Subjects
ELECTRONS, X-ray absorption, PHASE transitions, X-ray spectroscopy, CHARGE exchange, ELECTRON density
Abstract

X‐ray absorption spectroscopy (XAS) was used to elucidate changes in the electronic structure caused by the pressure‐induced structural collapse in EuCo2P2. The spectral changes observed at the L3‐edge of Eu and K‐edges of Co and P suggest electron density redistribution, which contradicts the formal charges calculated from the commonly used Zintl–Klemm concept. Quantum‐chemical calculations show that, despite the increase in the oxidation state of Eu and the formation of a weak P−P bond in the high‐pressure phase, the electron transfer from the Eu 4f orbitals to the hybridized 5d and 6s states causes strengthening of the Eu−P and P−P bonds. These changes explain the increased electron density on P atoms, deduced from the P K‐edge XAS spectra. This work shows that the formal electron counting schemes do not provide an adequate description of changes associated with phase transitions in metallic systems with substantial mixing of the electronic states. [ABSTRACT FROM AUTHOR]

Published
2019
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14. Magnetic asymmetry around the 3p absorption edge in Fe and Ni

Author

Locht, Inka L. M., Jana, Somnath, Kvashnin, Yaroslav O., Knut, Ronny, Di Marco, Igor, Chimata, Raghuveer, Malik, Rameez S., Ahlberg, Martina, Battiato, Marco, Rusz, Jan, Yaresko, Alexander N., Stefanuik, Robert, Söderström, Johan, Silva, Thomas, Åkerman, Johan, Nembach, Hans, Shaw, Justin, Karis, Olof, Eriksson, Olle, Locht, Inka L. M., Jana, Somnath, Kvashnin, Yaroslav O., Knut, Ronny, Di Marco, Igor, Chimata, Raghuveer, Malik, Rameez S., Ahlberg, Martina, Battiato, Marco, Rusz, Jan, Yaresko, Alexander N., Stefanuik, Robert, Söderström, Johan, Silva, Thomas, Åkerman, Johan, Nembach, Hans, Shaw, Justin, Karis, Olof, and Eriksson, Olle

Abstract

This work is a joint theoretical and experimental study of the relation between the magneto- optical response of a material in the sub-picosecond timescale and its instantaneous magnetisation. We perform pump-probe experiments in the transverse magneto-optical Kerr effect (T-MOKE) geometry. We measure the magnetic asymmetry of elemental Fe and Ni before and after the laser pulse. The observed differences between the magnetic asymmetry curves for various photon energies suggest that the relation between asymmetry and sample magnetization is more complex than a simple proportionality. Further insight is obtained by means of theoretical simulations based on density-functional theory. Our calculations show that non-linear effects in the asymmetry are most prominent at energies corresponding to the absorption edge and that the proportionality is recovered outside of this region. In conclusion, our experimental and theoretical results emphasize the need of including the complex relation between asymmetry and magnetization in the interpretation of ultrafast magnetization experiments in terms of microscopic properties.

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