Persistent nonequilibrium dynamics of the thermal energies in the spin and phonon systems of an antiferromagnet

Reppert, A. von; Pudell, J.; Koç, Azıze; Reinhardt, M.; Leitenberger, W.; Dumesnil, K.; Zamponi, F.; Bargheer, Matias

doi:10.1063/1.4961253

Cited by 26 publications

(39 citation statements)

References 36 publications

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The complexity of this interplay can leads to a variety of technologically useful behaviors. These effects include anomalous thermal expansion, 1,10,11 optical switching of magnetization, [11][12][13][14][15][16][17] and superconductivity. 18 Understanding the details of this electron-spinlattice interplay remains one of the most challenging scientific problems in condensed matter physics.…”

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confidence: 99%

Beyond a phenomenological description of magnetostriction

et al. 2018

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Magnetostriction, the strain induced by a change in magnetization, is a universal effect in magnetic materials. Owing to the difficulty in unraveling its microscopic origin, it has been largely treated phenomenologically. Here, we show how the source of magnetostriction—the underlying magnetoelastic stress—can be separated in the time domain, opening the door for an atomistic understanding. X-ray and electron diffraction are used to separate the sub-picosecond spin and lattice responses of FePt nanoparticles. Following excitation with a 50-fs laser pulse, time-resolved X-ray diffraction demonstrates that magnetic order is lost within the nanoparticles with a time constant of 146 fs. Ultrafast electron diffraction reveals that this demagnetization is followed by an anisotropic, three-dimensional lattice motion. Analysis of the size, speed, and symmetry of the lattice motion, together with ab initio calculations accounting for the stresses due to electrons and phonons, allow us to reveal the magnetoelastic stress generated by demagnetization.

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confidence: 99%

Beyond a phenomenological description of magnetostriction

et al. 2018

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“…Since the advent of femtosecond pulsed X-ray sources, lattice dynamics have been investigated on ultrafast time scales in a variety of different scientific contexts. [12][13][14][15] A first study of lattice dynamics accompanying ultrafast demagnetization was recently realized by Henighan et al 16 on a thin Fe film grown epitaxially on MgO. These authors observed THz frequency oscillations of the scat-tering intensities, which they attribute to the excitation of coherent longitudinal acoustic phonons building up the strain wave generated by the infrared (IR) excitation pulse.…”

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confidence: 99%

Structural dynamics during laser-induced ultrafast demagnetization

Jal¹,

López‐Flores²,

Pontius³

et al. 2017

Phys. Rev. B

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The mechanism underlying femtosecond laser pulse induced ultrafast magnetization dynamics remains elusive despite two decades of intense research on this phenomenon. Most experiments focused so far on characterizing magnetization and charge carrier dynamics, while first direct measurements of structural dynamics during ultrafast demagnetization were reported only very recently. We here present our investigation of the infrared laser pulse induced ultrafast demagnetization process in a thin Ni film, which characterizes simultaneously magnetization and structural dynamics. This is achieved by employing femtosecond time resolved X-ray resonant magnetic reflectivity (tr-XRMR) as probe technique. The experimental results reveal unambiguously that the sub-picosecond magnetization quenching is accompanied by strong changes in non-magnetic X-ray reflectivity. These changes vary with reflection angle and changes up to 30% have been observed. Modeling the X-ray reflectivity of the investigated thin film, we can reproduce these changes by a variation of the apparent Ni layer thickness of up to 1%. Extending these simulations to larger incidence angles we show that tr-XRMR can be employed to discriminate experimentally between currently discussed models describing the ultrafast demagnetization phenomenon.

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“…The exact temporal behavior of the measured average strain depends on the spatial form of the wave packet [12]. The strain beyond 50 ps arises from heating, which is proportional to the absorbed energy [1, 46,47]. Within our measurement window of 3 ns the thermal expansion shows almost no relaxation because of the slow heat transport out of Bi:YIG, as expected from the low thermal conductivity of garnet [48,49].…”

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confidence: 99%

Measurement of transient strain induced by two-photon excitation

Zeuschner

Pudell

Reppert

et al. 2020

Phys. Rev. Research

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By ultrafast x-ray diffraction we quantify the strain from coherent and incoherent phonons generated by one-and two-photon absorption. We investigated the ferrimagnetic insulator bismuth-doped yttrium iron garnet, which is a workhorse for laser-induced spin dynamics that may be excited indirectly via phonons. We identify the two-photon absorption by the quadratic intensity dependence of the transient strain and confirm a short lifetime of the intermediate state via the inverse proportional dependence on the pump-pulse duration. We determine the two-photon absorption coefficient using the linear relation between strain and absorbed energy density. For large intensities of about 1 TW/cm 2 considerable strain amplitudes of 0.1% are driven exclusively by two-photon absorption.

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Persistent nonequilibrium dynamics of the thermal energies in the spin and phonon systems of an antiferromagnet

Cited by 26 publications

References 36 publications

Beyond a phenomenological description of magnetostriction

Beyond a phenomenological description of magnetostriction

Structural dynamics during laser-induced ultrafast demagnetization

Measurement of transient strain induced by two-photon excitation

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