Energy- and crystal momentum-resolved study of laser-induced femtosecond magnetism

Zhang, G. P.; Bai, Yihua; George, Thomas F.

doi:10.1103/physrevb.80.214415

Cited by 36 publications

(49 citation statements)

References 37 publications

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“…This study reveals plenty of differences between the samples. In Gd 22 FeCo, F sw drops as the temperature decreases (similar dependence of F sw on temperature in the Gd 22 FeCo alloy was reported in Ref. 28).…”

Section: Efficiency Of the Helicity-dependent Reversalsupporting

confidence: 84%

“…If the switching was observed in M cases, then the probability of reversal for this particular set of conditions was taken as (100 M/N)%. The result for the sample Gd 22 FeCo is shown in Fig. 4(c), where these probabilities and the all-optical switchability, i.e., P(σ + ) − P(σ − ), are plotted as a function of the laser pulse fluence.…”

Section: Methodsmentioning

confidence: 99%

“…From the experimental point of view, studies of such a dynamics also require techniques that combine subpicosecond time resolution with a sensitivity to changes of the magnetic ordering. Consequently, attempts to understand ultrafast light-induced magnetization dynamics have yielded a burst in the development of various experimental [11][12][13][14][15][16][17] and theoretical [18][19][20][21][22][23] approaches (for a recent review, see Ref. 24).…”

Section: Introductionmentioning

confidence: 99%

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All-optical magnetization reversal by circularly polarized laser pulses: Experiment and multiscale modeling

et al. 2012

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We present results of detailed experimental and theoretical studies of all-optical magnetization reversal by single circularly-polarized laser pulses in ferrimagnetic rare earth-transition metal (RE-TM) alloys Gd x Fe 90−x Co 10 (20% < x < 28%). Using single-shot time-resolved magneto-optical microscopy and multiscale simulations, we identified and described the unconventional path followed by the magnetization during the reversal process. This reversal does not involve precessional motion of magnetization but is governed by the longitudinal relaxation and thus has a linear character. We demonstrate that this all-optically driven linear reversal can be modeled as a result of a two-fold impact of the laser pulse on the medium. First, due to absorption of the light and ultrafast laser-induced heating, the medium is brought to a highly nonequilibrium state. Simultaneously, due to the ultrafast inverse Faraday effect the circularly polarized laser pulse acts as an effective magnetic field of the amplitude up to ∼20 T. We show that the polarization-dependent reversal triggered by the circularly polarized light is feasible only in a narrow range (below 10%) of laser fluences. The duration of the laser pulse required for the reversal can be varied from ∼40 fs up to at least ∼1700 fs. We also investigate experimentally the role of the ferrimagnetic properties of GdFeCo in the all-optical reversal. In particular, the optimal conditions for the all-optical reversal are achieved just below the ferrimagnetic compensation temperature, where the magnetic information can be all-optically written by a laser pulse of minimal fluence and read out within just 30 ps. We argue that this is the fastest write-read event demonstrated for magnetic recording so far.

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Section: Efficiency Of the Helicity-dependent Reversalsupporting

confidence: 84%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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All-optical magnetization reversal by circularly polarized laser pulses: Experiment and multiscale modeling

et al. 2012

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“…Despite some controversy about the validity of MOKE as a probe of the magnetization of an excited system on the femtosecond timescale [4][5][6][7] , significant progress has been made: the importance of subtle effects, such as direct transfer of spin angular momentum 8 or coherent magneto-optical processes 9 , have been revealed. Phenomenological and microscopic models have been proposed and further refined [10][11][12][13] .…”

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confidence: 99%

Laser-induced ultrafast demagnetization in the presence of a nanoscale magnetic domain network

et al. 2012

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Femtosecond magnetization phenomena have been challenging our understanding for over a decade. most experiments have relied on infrared femtosecond lasers, limiting the spatial resolution to a few micrometres. With the advent of femtosecond X-ray sources, nanometric resolution can now be reached, which matches key length scales in femtomagnetism such as the travelling length of excited 'hot' electrons on a femtosecond timescale. Here we study laser-induced ultrafast demagnetization in [Co/Pd] 30 multilayer films, which, for the first time, achieves a spatial resolution better than 100 nm by using femtosecond soft X-ray pulses. This allows us to follow the femtosecond demagnetization process in a magnetic system consisting of alternating nanometric domains of opposite magnetization. no modification of the magnetic structure is observed, but, in comparison with uniformly magnetized systems of similar composition, we find a significantly faster demagnetization time. We argue that this may be caused by direct transfer of spin angular momentum between neighbouring domains.

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“…Finally, we compute the product of these two matrix elements. A lengthy but straightforward calculation 13 shows that for a transition with m j = 0 and j = 1, the expectation value of (SD) ab generator for this transition is…”

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confidence: 99%

Hot spin spots in the laser-induced demagnetization

Zhang

2012

AIP Advances

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Laser-induced femtosecond magnetism or femtomagnetism simultaneously relies on two distinctive contributions: (a) the optical dipole interaction (ODI) between a laser field and a magnetic system and (b) the spin expectation value change (SEC) between two transition states. Surprisingly, up to now, no study has taken both contributions into account simultaneously. Here we do so by introducing a new concept of the optical spin generator, a product of SEC and ODI between transition states. In ferromagnetic nickel, our first-principles calculation demonstrates that the larger the value of optical spin generator is, the larger the dynamic spin moment change is. This simple generator directly links the time-dependent spin moment change Δ M z k (t) at every crystal-momentum k point to its intrinsic electronic structure and magnetic properties. Those hot spin spots are a direct manifestation of the optical spin generator, and should be the focus of future research

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Energy- and crystal momentum-resolved study of laser-induced femtosecond magnetism

Cited by 36 publications

References 37 publications

All-optical magnetization reversal by circularly polarized laser pulses: Experiment and multiscale modeling

All-optical magnetization reversal by circularly polarized laser pulses: Experiment and multiscale modeling

Laser-induced ultrafast demagnetization in the presence of a nanoscale magnetic domain network

Hot spin spots in the laser-induced demagnetization

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