Element-resolved ultrafast demagnetization rates in ferrimagnetic CoDy

Ferté, Tom; Bergeard, Nicolas; Guyader, Löic Le; Hehn, Michel; Malinowski, Grégory; Terrier, Erwan; Otero, Edwige; Holldack, K.; Pontius, N.; Boeglin, C.

doi:10.1103/physrevb.96.134303

Cited by 13 publications

(16 citation statements)

References 80 publications

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“…We remark that the different compensation temperatures of our two CoDy alloys seem not to play a role here as demonstrated previously by Ferté et al 31 .…”

Section: Discussionsupporting

confidence: 83%

Single-shot time-resolved magnetic x-ray absorption at a free-electron laser

et al. 2019

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Ultrafast dynamics are generally investigated using stroboscopic pump-probe measurements, which characterize the sample properties for a single, specific time delay. These measurements are then repeated for a series of discrete time delays to reconstruct the overall time trace of the process. As a consequence, this approach is limited to the investigation of fully reversible phenomena. We recently introduced an off-axis zone plate based X-ray streaking technique, which overcomes this limitation by sampling the relaxation dynamics with a single femtosecond X-ray pulse streaked over a picosecond long time window. In this article we show that the X-ray absorption cross section can be employed as the contrast mechanism in this novel technique. We show that changes of the absorption cross section on the percent level can be resolved with this method. To this end we measure the ultrafast magnetization dynamics in CoDy alloy films. Investigating different chemical compositions and infrared pump fluences, we demonstrate the routine applicability of this technique. Probing in transmission the average magnetization dynamics of the entire film, our experimental findings indicate that the demagnetization time is independent of the specific infrared laser pump fluence. These results pave the way for the investigation of irreversible phenomena in a wide variety of scientific areas.

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“…We remark that the different compensation temperatures of our two CoDy alloys seem not to play a role here as demonstrated previously by Ferté et al 31 .…”

Section: Discussionsupporting

confidence: 83%

Single-shot time-resolved magnetic x-ray absorption at a free-electron laser

et al. 2019

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“…As discussed in the theoretical part, for only one direction of the magnetization, the intensity recorded and shown on this curve is related to the magnetization but not directly proportional to it. We can nevertheless fit our data with a double exponential expression based on a semi-empirical model [32] to extract a rough estimate of the demagnetization time: in this case about 200 fs, in agreement with recent reports on magnetization dynamics in CoDy [33]. These first results prove the capability of our technique to follow magnetization dynamics.…”

Section: Resultssupporting

confidence: 88%

Resonant Faraday effect using high-order harmonics for the investigation of ultrafast demagnetization

et al. 2019

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During the past few years high-order harmonic generation (HHG) has opened up the field of ultrafast spectroscopy to an ever larger community by providing a table-top and affordable femtosecond extreme ultraviolet (EUV) and soft-x-ray source. In particular, the field of femtomagnetism has largely benefited from the development of these sources. However, the use of x-ray magnetic circular dichroism (XMCD) as a probe of magnetization, the most versatile and reliable one, has been constrained by the lack of polarization control at HHG sources, so studies have relied on more specific magneto-optical effects. Even the recent developments on the generation of elliptically polarized harmonics have only resulted in a few time-resolved experiments relying on this powerful technique since they add complexity to already-difficult measurements. In this article we show how to easily probe magnetization dynamics with linearly polarized EUV or soft-x-ray light with a versatility similar to XMCD by exploiting the Faraday effect. Static and time-resolved measurements of the Faraday effect are presented around the Co M edges. Using simple theoretical considerations, we show how to retrieve the samples magnetization dynamics from the Faraday rotation and ellipticity transients. Ultrafast demagnetization dynamics of a few nanometers in Co-based samples are measured with this method in out-of-plane as well as in-plane magnetization configurations, showing its great potential for the study of femtomagnetism.

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“…Comparing our demagnetization times with recent measurements on amorphous CoDy alloys, we find, however, similar values for τ D . [29] Now, we turn to the comparison of the experimental and theoretical results. We obtain distinct, element-specific damping parameters of α el Co ¼ 0.004 and α Dy ¼ 0.03 by minimizing the mean squared error between the combined Dy and Co XMCD data and the ASD simulation results, both displayed in Figure 2.…”

Section: Element-specific Magnetization Dynamicsmentioning

confidence: 99%

Element‐Specific Magnetization Damping in Ferrimagnetic DyCo₅ Alloys Revealed by Ultrafast X‐ray Measurements

Abrudan

Hennecke

Radu

et al. 2021

Physica Rapid Research Ltrs

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The dynamic response of magnetically ordered materials to an ultrashort external stimulus depends on microscopic parameters, such as magnetic moment, exchange, and spin–orbit interactions. Whereas it is well established that, in multicomponent magnetic alloys and compounds, the speed of demagnetization and spin switching processes has an element‐specific character, the magnetization damping was assumed to be a universal parameter for all constituent magnetic elements irrespective of their different spin–orbit couplings and electronic structure. Herein, experimental and theoretical evidence for an element‐specific magnetic damping parameter is provided by investigating the ultrafast magnetization response of a high‐anisotropy ferrimagnetic DyCo5 alloy to femtosecond laser excitation. Strikingly different demagnetization and remagnetization dynamics of Dy and Co magnetic moments is revealed by employing femtosecond laser pump–X‐ray magnetic circular dichroism probe measurements combined with atomistic spin dynamics (ASD) simulations using ab initio calculated parameters. These observations, fully corroborated by the ASD simulations, are linked to the element‐specific spin–orbit coupling strengths of Dy and Co, which are incorporated in the phenomenological magnetization damping parameters. These findings can be used as a recipe for tuning the speed and magnitude of laser‐driven magnetic processes and consequently allow control over various dynamic functionalities in multicomponent magnetic materials.

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Element-resolved ultrafast demagnetization rates in ferrimagnetic CoDy

Cited by 13 publications

References 80 publications

Single-shot time-resolved magnetic x-ray absorption at a free-electron laser

Single-shot time-resolved magnetic x-ray absorption at a free-electron laser

Resonant Faraday effect using high-order harmonics for the investigation of ultrafast demagnetization

Element‐Specific Magnetization Damping in Ferrimagnetic DyCo₅ Alloys Revealed by Ultrafast X‐ray Measurements

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Element-resolved ultrafast demagnetization rates in ferrimagnetic CoDy

Cited by 13 publications

References 80 publications

Single-shot time-resolved magnetic x-ray absorption at a free-electron laser

Single-shot time-resolved magnetic x-ray absorption at a free-electron laser

Resonant Faraday effect using high-order harmonics for the investigation of ultrafast demagnetization

Element‐Specific Magnetization Damping in Ferrimagnetic DyCo5 Alloys Revealed by Ultrafast X‐ray Measurements

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Product

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Element‐Specific Magnetization Damping in Ferrimagnetic DyCo₅ Alloys Revealed by Ultrafast X‐ray Measurements