Publications of Thomas Ostler
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See detailMultiscale Modeling of Ultrafast Magnetization Dynamics
Ostler, Thomas ULiege; Barker, J.; Evans, R. F. L. et al

in Ultrafast Magnetism I (2014)

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See detailTwo-magnon bound state causes ultrafast thermally induced magnetisation switching
Barker, J.; Atxitia, U.; Ostler, Thomas ULiege et al

in Scientific Reports (2013), 3

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See detailUltrafast dynamical path for the switching of a ferrimagnet after femtosecond heating
Atxitia, U.; Ostler, Thomas ULiege; Barker, J. et al

in Physical Review B (2013), 87(22),

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See detailComputer Simulations of Ultrafast Magnetisation Reversal
Ostler, Thomas ULiege

Doctoral thesis (2012)

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See detailClassical spin model of the relaxation dynamics of rare-earth doped permalloy
Ellis, M. O. A.; Ostler, Thomas ULiege; Chantrell, R. W.

in Physical Review B (2012), 86(17),

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See detailUltrafast heating as a sufficient stimulus for magnetization reversal in a ferrimagnet
Ostler, Thomas ULiege; Barker, J.; Evans, R. F. L. et al

in Nature Communications (2012), 3

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See detailUltrafast Magnetism as Seen by X-rays
Radu, Ilie; Vahaplar, Kadir; Stamm, Christian et al

in ULTRAFAST PHENOMENA AND NANOPHOTONICS XVI (2012)

Revealing the ultimate speed limit at which magnetic order can be controlled, is a fundamental challenge of modern magnetism having far reaching implications for magnetic recording industry. Exchange ... [more ▼]

Revealing the ultimate speed limit at which magnetic order can be controlled, is a fundamental challenge of modern magnetism having far reaching implications for magnetic recording industry. Exchange interaction is the strongest force in magnetism, being responsible for ferromagnetic or antiferromagnetic spin order. How do spins react after being optically perturbed on an ultrashort timescales pertinent to the characteristic time of the exchange interaction? Here we demonstrate that femtosecond measurements of X-ray magnetic circular dichroism provide revolutionary new insights into the problem of ultrafast magnetism. In particular, we show that upon femtosecond optical excitation the ultrafast spin reversal of Gd(FeCo) - a material with antiferromagnetic coupling of spins - occurs via a transient ferromagnetic state. The latter one emerges due to different dynamics of Gd and Fe magnetic moments: Gd switches within 1.5 ps while it takes only 300 fs for Fe. Thus, by using a single fs laser pulse one can force the spin system to evolve via an energetically unfavorable way and temporary switch from an antiferromagnetic to ferromagnetic type of ordering. These observations supported by atomistic simulations, present a novel concept of manipulating magnetic order on different classes of magnetic materials on timescales of the exchange interaction. [less ▲]

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See detailTransient ferromagnetic-like state mediating ultrafast reversal of antiferromagnetically coupled spins
Radu, I.; Vahaplar, K.; Stamm, C. et al

in NATURE (2011), 472(7342), 205-208

Ferromagnetic or antiferromagnetic spin ordering is governed by the exchange interaction, the strongest force in magnetism(1-4). Understanding spin dynamics in magnetic materials is an issue of crucial ... [more ▼]

Ferromagnetic or antiferromagnetic spin ordering is governed by the exchange interaction, the strongest force in magnetism(1-4). Understanding spin dynamics in magnetic materials is an issue of crucial importance for progress in information processing and recording technology. Usually the dynamics are studied by observing the collective response of exchange-coupled spins, that is, spin resonances, after an external perturbation by a pulse of magnetic field, current or light. The periods of the corresponding resonances range from one nanosecond for ferromagnets down to one picosecond for antiferromagnets. However virtually nothing is known about the behaviour of spins in a magnetic material after being excited on a timescale faster than that corresponding to the exchange interaction (10-100 fs), that is, in a non-adiabatic way. Here we use the element-specific technique X-ray magnetic circular dichroism to study spin reversal in GdFeCo that is optically excited on a timescale pertinent to the characteristic time of the exchange interaction between Gd and Fe spins. We unexpectedly find that the ultrafast spin reversal in this material, where spins are coupled antiferromagnetically, occurs by way of a transient ferromagnetic-like state. Following the optical excitation, the net magnetizations of the Gd and Fe sublattices rapidly collapse, switch their direction and rebuild their net magnetic moments at substantially different timescales; the net magnetic moment of the Gd sublattice is found to reverse within 1.5 picoseconds, which is substantially slower than the Fe reversal time of 300 femtoseconds. Consequently, a transient state characterized by a temporary parallel alignment of the net Gd and Fe moments emerges, despite their ground-state antiferromagnetic coupling. These surprising observations, supported by atomistic simulations, provide a concept for the possibility of manipulating magnetic order on the timescale of the exchange interaction. [less ▲]

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See detailAn X-ray view on ultrafast magnetization switching of GdFeCo
Radu, Ilie; Vahaplar, Kadir; Kirilyuk, Andrei et al

Conference (2011)

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See detailCrystallographically amorphous ferrimagnetic alloys: Comparing a localized atomistic spin model with experiments
Ostler, Thomas ULiege; Evans, Richard F. L.; Chantrell, Roy W. et al

in PHYSICAL REVIEW B (2011), 84(2),

We present a computational model of crystallographically amorphous ferrimagnetic alloys using a stochastic Landau-Lifshitz-Gilbert equation of motion for atomistic spins and an atomistic spin Hamiltonian ... [more ▼]

We present a computational model of crystallographically amorphous ferrimagnetic alloys using a stochastic Landau-Lifshitz-Gilbert equation of motion for atomistic spins and an atomistic spin Hamiltonian with Heisenberg exchange. The spontaneous equilibrium magnetization is calculated and a comparison with a mean field model is made. The simulations show excellent agreement with experiments on GdFeCo using x-ray magnetic circular dichroism to determine the individual sublattice magnetizations. The calculated temperature dependence of the magnetization shows a polarization of the Gd sublattice leading to a common Curie temperature, in agreement with the experimental data. The intersublattice exchange is shown to be an important energy transfer channel for ultrafast dynamics. [less ▲]

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