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7 results on '"Mendil, J."'

1. Speed limit of FePt spin dynamics on femtosecond timescales

Author

Mendil, J., Nieves, P. C., Chubykalo-Fesenko, O., Walowski, J., Münzenberg, M., Santos, T., and Pisana, S.

Subjects
Condensed Matter - Materials Science
Abstract

Magnetization manipulation is becoming an indispensable tool for both basic and applied research. Theory predicts two types of ultrafast demagnetization dynamics classified as type I and type II. In type II materials, a second slower process takes place after the initial fast drop of magnetization. In this letter we investigate this behavior for FePt recording materials with perpendicular anisotropy. The magnetization dynamics have been simulated using a thermal micromagnetic model based on the Landau-Lifshitz-Bloch equation. We identify a transition to type II behavior and relate it to the electron temperatures reached by the laser heating. This slowing down is a fundamental limit to reconding speeds in heat assisted reversal., Comment: 14 pages, 5 figures

Published
2013
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4. Resolving the role of femtosecond heated electrons in ultrafast spin dynamics

Author

Mendil, J., Nieves, Pablo, Chubykalo-Fesenko, O., Walowski, J., Santos, T., Pisana, S., Münzenberg, M., European Commission, and Ministerio de Ciencia e Innovación (España)

Subjects
Ferromagnetism, Ultrafast photonics, Spintronics, Condensed Matter::Strongly Correlated Electrons, Article
Abstract

This work is licensed under a Creative Commons Attribution 3.0 Unported license., Magnetization manipulation is essential for basic research and applications. A fundamental question is, how fast can the magnetization be reversed in nanoscale magnetic storage media. When subject to an ultrafast laser pulse, the speed of the magnetization dynamics depends on the nature of the energy transfer pathway. The order of the spin system can be effectively influenced through spin-flip processes mediated by hot electrons. It has been predicted that as electrons drive spins into the regime close to almost total demagnetization, characterized by a loss of ferromagnetic correlations near criticality, a second slower demagnetization process takes place after the initial fast drop of magnetization. By studying FePt, we unravel the fundamental role of the electronic structure. As the ferromagnet Fe becomes more noble in the FePt compound, the electronic structure is changed and the density of states around the Fermi level is reduced, thereby driving the spin correlations into the limit of critical fluctuations. We demonstrate the impact of the electrons and the ferromagnetic interactions, which allows a general insight into the mechanisms of spin dynamics when the ferromagnetic state is highly excited, and identifies possible recording speed limits in heat-Assisted magnetization reversal., Research at Göttingen University was supported by German Research Foundation (DFG) through Research at Göttingen University was supported by German Research Foundation (DFG) through MU 1780/ 6-1 Photo-Magnonics, SPP 1538 SpinCaT and SFB 1073. Research in Madrid was supported by the European Community's Seventh Framework Programme under grant agreement NNP3-SL-2012-281043 (FEMTOSPIN) and the Spanish Ministry of Science and Innovation under the grant FIS2010-20979-C02-02. We acknowledge support by the German Research Foundation and the Open Access Publication Funds of the Göttingen University.

Published
2014

5. Resolving the role of femtosecond heated electrons in ultrafast spin dynamics

Author

European Commission, Ministerio de Ciencia e Innovación (España), Mendil, J., Nieves, Pablo, Chubykalo-Fesenko, O., Walowski, J., Santos, T., Pisana, S., Münzenberg, M., European Commission, Ministerio de Ciencia e Innovación (España), Mendil, J., Nieves, Pablo, Chubykalo-Fesenko, O., Walowski, J., Santos, T., Pisana, S., and Münzenberg, M.

Abstract

Magnetization manipulation is essential for basic research and applications. A fundamental question is, how fast can the magnetization be reversed in nanoscale magnetic storage media. When subject to an ultrafast laser pulse, the speed of the magnetization dynamics depends on the nature of the energy transfer pathway. The order of the spin system can be effectively influenced through spin-flip processes mediated by hot electrons. It has been predicted that as electrons drive spins into the regime close to almost total demagnetization, characterized by a loss of ferromagnetic correlations near criticality, a second slower demagnetization process takes place after the initial fast drop of magnetization. By studying FePt, we unravel the fundamental role of the electronic structure. As the ferromagnet Fe becomes more noble in the FePt compound, the electronic structure is changed and the density of states around the Fermi level is reduced, thereby driving the spin correlations into the limit of critical fluctuations. We demonstrate the impact of the electrons and the ferromagnetic interactions, which allows a general insight into the mechanisms of spin dynamics when the ferromagnetic state is highly excited, and identifies possible recording speed limits in heat-Assisted magnetization reversal.

Published
2014

6. Origins of the Unidirectional Spin Hall Magnetoresistance in Metallic Bilayers.

Author

Avci CO, Mendil J, Beach GSD, and Gambardella P

Abstract

Recent studies evidenced the emergence of asymmetric electron transport in layered conductors owing to the interplay between electrical conductivity, magnetization, and the spin Hall or Rashba-Edelstein effects. Here, we investigate the unidirectional magnetoresistance (UMR) caused by the current-induced spin accumulation in Co/Pt and CoCr/Pt bilayers. We identify three competing mechanisms underpinning the resistance asymmetry, namely, interface and bulk spin-dependent electron scattering and electron-magnon scattering. Our measurements provide a consistent description of the current, magnetic field, and temperature dependence of the UMR and show that both positive and negative UMR can be obtained by tuning the interface and bulk spin-dependent scattering.

Published
2018
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7. Spatially and time-resolved magnetization dynamics driven by spin-orbit torques.

Author

Baumgartner M, Garello K, Mendil J, Avci CO, Grimaldi E, Murer C, Feng J, Gabureac M, Stamm C, Acremann Y, Finizio S, Wintz S, Raabe J, and Gambardella P

Abstract

Current-induced spin-orbit torques are one of the most effective ways to manipulate the magnetization in spintronic devices, and hold promise for fast switching applications in non-volatile memory and logic units. Here, we report the direct observation of spin-orbit-torque-driven magnetization dynamics in Pt/Co/AlO x dots during current pulse injection. Time-resolved X-ray images with 25 nm spatial and 100 ps temporal resolution reveal that switching is achieved within the duration of a subnanosecond current pulse by the fast nucleation of an inverted domain at the edge of the dot and propagation of a tilted domain wall across the dot. The nucleation point is deterministic and alternates between the four dot quadrants depending on the sign of the magnetization, current and external field. Our measurements reveal how the magnetic symmetry is broken by the concerted action of the damping-like and field-like spin-orbit torques and the Dzyaloshinskii-Moriya interaction, and show that reproducible switching events can be obtained for over 10 12 reversal cycles.

Published
2017
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