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BETA
Battiato, Marco
Publications (10 of 16) Show all publications
Rudolf, D., La-O-Vorakiat, C., Battiato, M., Adam, R., Grychtol, P., Shaw, J. M., . . . Schneider, C. M. (2015). Element Selective Investigation of Spin Dynamics in Magnetic Multilayers. In: Bigot, JY; Hubner, W; Rasing, T; Chantrell, R (Ed.), Ultrafast Magnetism I: . Paper presented at Ultrafast Magnetization Conference, OCT 28-NOV 01, 2013, Strasbourg, FRANCE (pp. 307-309).
Open this publication in new window or tab >>Element Selective Investigation of Spin Dynamics in Magnetic Multilayers
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2015 (English)In: Ultrafast Magnetism I / [ed] Bigot, JY; Hubner, W; Rasing, T; Chantrell, R, 2015, p. 307-309Conference paper, Published paper (Refereed)
Abstract [en]

Our understanding of ultrafast switching processes in novel spin-based electronics depends on our detailed knowledge of interactions between spin, charge and phonons in magnetic structures. We present element-selective studies, using extreme ultraviolet (XUV) light, to gain insight into spin dynamics in exchange coupled magnetic multilayers on the femtosecond time scale.

Series
Springer Proceedings in Physics, ISSN 0930-8989 ; 159
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-309671 (URN)10.1007/978-3-319-07743-7_95 (DOI)000349745400095 ()9783319077437 (ISBN)9783319077420 (ISBN)
Conference
Ultrafast Magnetization Conference, OCT 28-NOV 01, 2013, Strasbourg, FRANCE
Available from: 2016-12-06 Created: 2016-12-06 Last updated: 2016-12-06Bibliographically approved
Carva, K., Battiato, M., Legut, D. & Oppeneer, P. M. (2015). Theory of femtosecond laser-induced demagnetization. In: ULTRAFAST MAGNETISM I: . Paper presented at Ultrafast Magnetization Conference, OCT 28-NOV 01, 2013, Strasbourg, FRANCE (pp. 111-115).
Open this publication in new window or tab >>Theory of femtosecond laser-induced demagnetization
2015 (English)In: ULTRAFAST MAGNETISM I, 2015, p. 111-115Conference paper, Published paper (Refereed)
Abstract [en]

Using ab initio calculations we computed the ultrafast demagnetization that can be achieved by Elliott-Yafet electron-phonon spin-flip scatterings in laser-excited ferromagnets. Our calculations show that nonequilibrium laser-created distributions contribute mostly to the ultrafast demagnetization. Nonetheless, the total Elliott-Yafet contribution is too small to account for the fs-demagnetization.

Series
Springer Proceedings in Physics, ISSN 0930-8989 ; 159
National Category
Other Physics Topics
Identifiers
urn:nbn:se:uu:diva-249063 (URN)10.1007/978-3-319-07743-7_36 (DOI)000349745400036 ()978-3-319-07743-7 (ISBN)978-3-319-07742-0 (ISBN)
Conference
Ultrafast Magnetization Conference, OCT 28-NOV 01, 2013, Strasbourg, FRANCE
Available from: 2015-04-20 Created: 2015-04-10 Last updated: 2015-04-20Bibliographically approved
Kampfrath, T., Battiato, M., Sell, A., Freimuth, F., Leitenstorfer, A., Wolf, M., . . . Muenzenberg, M. (2015). Ultrafast spin precession and transport controlled and probed with terahertz radiation. In: Bigot, JY; Hubner, W; Rasing, T; Chantrell, R (Ed.), Ultrafast Magnetism I: . Paper presented at Ultrafast Magnetization Conference, OCT 28-NOV 01, 2013, Strasbourg, FRANCE (pp. 324-326).
Open this publication in new window or tab >>Ultrafast spin precession and transport controlled and probed with terahertz radiation
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2015 (English)In: Ultrafast Magnetism I / [ed] Bigot, JY; Hubner, W; Rasing, T; Chantrell, R, 2015, p. 324-326Conference paper, Published paper (Refereed)
Abstract [en]

We present examples of how terahertz (THz) electromagnetic transients can be used to control spin precession in antiferromagnets (through the THz Zeeman torque) and to probe spin transport in magnetic heterostructures (through the THz inverse spin Hall effect), on femtosecond time scales.

Series
Springer Proceedings in Physics, ISSN 0930-8989 ; 159
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-309672 (URN)10.1007/978-3-319-07743-7_100 (DOI)000349745400100 ()9783319077437 (ISBN)9783319077420 (ISBN)
Conference
Ultrafast Magnetization Conference, OCT 28-NOV 01, 2013, Strasbourg, FRANCE
Available from: 2016-12-06 Created: 2016-12-06 Last updated: 2016-12-06Bibliographically approved
Eschenlohr, A., Battiato, M., Maldonado, P., Pontius, N., Kachel, T., Holldack, K., . . . Stamm, C. (2014). Optical excitation of thin magnetic layers in multilayer structures Reply [Letter to the editor]. Nature Materials, 13(2), 102-103
Open this publication in new window or tab >>Optical excitation of thin magnetic layers in multilayer structures Reply
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2014 (English)In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 13, no 2, p. 102-103Article in journal, Letter (Refereed) Published
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-219409 (URN)10.1038/nmat3851 (DOI)000330182700003 ()
Available from: 2014-03-06 Created: 2014-02-28 Last updated: 2017-12-05Bibliographically approved
Battiato, M., Barbalinardo, G. & Oppeneer, P. M. (2014). Quantum theory of the inverse Faraday effect. Physical Review B. Condensed Matter and Materials Physics, 89(1), 014413
Open this publication in new window or tab >>Quantum theory of the inverse Faraday effect
2014 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 1, p. 014413-Article in journal (Refereed) Published
Abstract [en]

We provide a quantum theoretical description of the magnetic polarization induced by intense circularly polarized light in a material. Such effect-commonly referred to as the inverse Faraday effect-is treated using beyond-linear response theory, considering the applied electromagnetic field as external perturbation. An analytical time-dependent solution of the Liouville-von Neumann equation to second order is obtained for the density matrix and used to derive expressions for the optomagnetic polarization. Two distinct cases are treated, the long-time adiabatic limit of polarization imparted by continuous wave irradiation, and the full temporal shape of the transient magnetic polarization induced by a short laser pulse. We further derive expressions for the Verdet constants for the inverse, optomagnetic Faraday effect and for the conventional, magneto-optical Faraday effect and show that they are in general different. Additionally, we derive expressions for the Faraday and inverse Faraday effects within the Drude-Lorentz theory and demonstrate that their equality does not hold in general, but only for dissipationless media. As an example, we perform initial quantum mechanical calculations of the two Verdet constants for a hydrogenlike atom and we extract the trends. We observe that one reason for a large inverse Faraday effect in heavy atoms is the spatial extension of the wave functions rather than the spin-orbit interaction, which nonetheless contributes positively.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-221942 (URN)10.1103/PhysRevB.89.014413 (DOI)000332211200002 ()
Available from: 2014-04-07 Created: 2014-04-07 Last updated: 2017-12-05Bibliographically approved
Battiato, M., Maldonado, P. & Oppeneer, P. M. (2014). Treating the effect of interface reflections on superdiffusive spin transport in multilayer samples (invited). Journal of Applied Physics, 115(17), 172611
Open this publication in new window or tab >>Treating the effect of interface reflections on superdiffusive spin transport in multilayer samples (invited)
2014 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 17, p. 172611-Article in journal (Refereed) Published
Abstract [en]

Femtosecond laser-induced magnetization dynamics has recently been related to superdiffusive spin transport. With the aim to accurately compute spin superdiffusion in the complex geometries of layered heterostructures and free standing layers, we develop here a dedicated numerical scheme. We introduce a discretization technique to solve the superdiffusive equation numerically on a time and space grid. The discretization scheme facilitates an explicit treatment of the total reflection at the vacuum-material surfaces as well as of partial reflections at the interfaces between two different materials. The advantages of the numerical technique are discussed. (C) 2014 AIP Publishing LLC.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-227177 (URN)10.1063/1.4870589 (DOI)000335643700580 ()
Available from: 2014-06-27 Created: 2014-06-24 Last updated: 2017-12-05Bibliographically approved
Carva, K., Battiato, M., Legut, D. & Oppeneer, P. M. (2013). Ab initio theory of electron-phonon mediated ultrafast spin relaxation of laser-excited hot electrons in transition-metal ferromagnets. Physical Review B. Condensed Matter and Materials Physics, 87(18), 184425
Open this publication in new window or tab >>Ab initio theory of electron-phonon mediated ultrafast spin relaxation of laser-excited hot electrons in transition-metal ferromagnets
2013 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 18, p. 184425-Article in journal (Refereed) Published
Abstract [en]

We report a computational theoretical investigation of electron spin-flip scattering induced by the electron-phonon interaction in the transition-metal ferromagnets bcc Fe, fcc Co, and fcc Ni. The Elliott-Yafet electron-phonon spin-flip scattering is computed from first principles, employing a generalized spin-flip Eliashberg function as well as ab initio computed phonon dispersions. Aiming at investigating the amount of electron-phonon mediated demagnetization in femtosecond laser-excited ferromagnets, the formalism is extended to treat laser-created thermalized as well as nonequilibrium, nonthermal hot electron distributions. Using the developed formalism we compute the phonon-induced spin lifetimes of hot electrons in Fe, Co, and Ni. The electron-phonon mediated demagnetization rate is evaluated for laser-created thermalized and nonequilibrium electron distributions. Nonthermal distributions are found to lead to a stronger demagnetization rate than hot, thermalized distributions, yet their demagnetizing effect is not enough to explain the experimentally observed demagnetization occurring in the subpicosecond regime.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-203293 (URN)10.1103/PhysRevB.87.184425 (DOI)000319280800002 ()
Available from: 2013-07-09 Created: 2013-07-08 Last updated: 2017-12-06Bibliographically approved
Battiato, M. (2013). Superdiffusive Spin Transport and Ultrafast Magnetization Dynamics: Femtosecond spin transport as the route to ultrafast spintronics. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Superdiffusive Spin Transport and Ultrafast Magnetization Dynamics: Femtosecond spin transport as the route to ultrafast spintronics
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The debate over the origin of the ultrafast demagnetization has been intensively active for the past 16 years. Several microscopic mechanisms have been proposed but none has managed so far to provide direct and incontrovertible evidences of their validity. In this context I have proposed an approach based on spin dependent electron superdiffusion as the driver of the ultrafast demagnetization.

Excited electrons and holes in the ferromagnetic metal start diffusing after the absorption of the laser photons. Being the material ferromagnetic, the majority and minority spin channels occupy very different bands. It is then not surprising that transport properties are strongly spin dependent. In most of the ferromagnetic metals, majority spin excited electrons have better transport properties than minority ones. The effect is that majority carriers are more efficient in leaving the area irradiated by the laser, triggering a net spin transport.

Recent experimental findings are revolutionising the field by being incompatible with previously proposed models and showing uncontrovertibly the sign of spin superdiffusion.

We have shown that spin diffusing away from a layer undergoing ultrafast demagnetization can be used to create an ultrafast increase of magnetization in a neighboring magnetic layer. We have also shown that optical excitation is not a prerequisite for the ultrafast demagnetization and that excited electrons superdiffusing from a non-magnetic substrate can trigger the demagnetization. Finally we have shown that it is possible to control the time shape of the spin currents created and developed a technique to detect directly spin currents in a contact-less way. 

The impact of these new discoveries goes beyond the solution of the mystery of ultrafast demagnetization. It shows how spin information can be, not only manipulated, as shown 16 years ago, but most importantly transferred at unprecedented speeds. This new discovery lays the basis for a full femtosecond spintronics.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. p. 64
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1061
Keywords
Ultrafast magnetisation dynamics, anomalous diffusion, femtosecond dynamics, magnetism
National Category
Condensed Matter Physics
Research subject
Materials Science
Identifiers
urn:nbn:se:uu:diva-205265 (URN)978-91-554-8722-5 (ISBN)
Public defence
2013-09-27, Siegbahnsalen, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2013-09-06 Created: 2013-08-15 Last updated: 2014-01-08
Kampfrath, T., Battiato, M., Maldonado, P., Eilers, G., Noetzold, J., Maehrlein, S., . . . Muenzenberg, M. (2013). Terahertz spin current pulses controlled by magnetic heterostructures. Nature Nanotechnology, 8(4), 256-260
Open this publication in new window or tab >>Terahertz spin current pulses controlled by magnetic heterostructures
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2013 (English)In: Nature Nanotechnology, ISSN 1748-3387, E-ISSN 1748-3395, Vol. 8, no 4, p. 256-260Article in journal (Refereed) Published
Abstract [en]

In spin-based electronics, information is encoded by the spin state of electron bunches(1-4). Processing this information requires the controlled transport of spin angular momentum through a solid(5,6), preferably at frequencies reaching the so far unexplored terahertz regime(7-9). Here, we demonstrate, by experiment and theory, that the temporal shape of femtosecond spin current bursts can be manipulated by using specifically designed magnetic heterostructures. A laser pulse is used to drive spins(10-12) from a ferromagnetic iron thin film into a non-magnetic cap layer that has either low (ruthenium) or high (gold) electron mobility. The resulting transient spin current is detected by means of an ultrafast, contactless amperemeter(13) based on the inverse spin Hall effect(14,15), which converts the spin flow into a terahertz electromagnetic pulse. We find that the ruthenium cap layer yields a considerably longer spin current pulse because electrons are injected into ruthenium d states, which have a much lower mobility than gold sp states(16). Thus, spin current pulses and the resulting terahertz transients can be shaped by tailoring magnetic heterostructures, which opens the door to engineering high-speed spintronic devices and, potentially, broadband terahertz emitters(7-9).

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-199719 (URN)10.1038/NNANO.2013.43 (DOI)000317046800011 ()
Available from: 2013-05-13 Created: 2013-05-13 Last updated: 2017-12-06Bibliographically approved
Eschenlohr, A., Battiato, M., Maldonado, P., Pontius, N., Kachel, T., Holldack, K., . . . Stamm, C. (2013). Ultrafast spin transport as key to femtosecond demagnetization. Nature Materials, 12(4), 332-336
Open this publication in new window or tab >>Ultrafast spin transport as key to femtosecond demagnetization
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2013 (English)In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 12, no 4, p. 332-336Article in journal (Refereed) Published
Abstract [en]

Irradiating a ferromagnet with a femtosecond laser pulse is known to induce an ultrafast demagnetization within a few hundred femtoseconds. Here we demonstrate that direct laser irradiation is in fact not essential for ultrafast demagnetization, and that electron cascades caused by hot electron currents accomplish it very efficiently. We optically excite a Au/Ni layered structure in which the 30 nm Au capping layer absorbs the incident laser pump pulse and subsequently use the X-ray magnetic circular dichroism technique to probe the femtosecond demagnetization of the adjacent 15 nm Ni layer. A demagnetization effect corresponding to the scenario in which the laser directly excites the Ni film is observed, but with a slight temporal delay. We explain this unexpected observation by means of the demagnetizing effect of a superdiffusive current of non-equilibrium, non-spin-polarized electrons generated in the Au layer.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-199718 (URN)10.1038/NMAT3546 (DOI)000317164900022 ()
Available from: 2013-05-13 Created: 2013-05-13 Last updated: 2017-12-06Bibliographically approved
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