Time-resolved surface magnetometry in the nanosecond scale using synchrotron radiation

Sirotti, Fausto; Bosshard, R.; Prieto, Pilar; Panaccione, G.; Floreano, Luca; Jucha, A.; Bellier, J. D.; Rossi, G.

doi:10.1063/1.366866

Cited by 23 publications

(17 citation statements)

References 17 publications

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“…Recent efforts to use pulsed x-ray sources for time-resolved spin polarized photoemission measurements have been fruitful. 26 However, both such techniques are expensive and complex to implement. The inductive method presented here is much simpler, both in design and in use, with the exception of our use of a mode-locked Ti:sapphire laser as part of the impulse generator.…”

Section: Discussionmentioning

confidence: 99%

Inductive measurement of ultrafast magnetization dynamics in thin-film Permalloy

Silva

Lee

Crawford

et al. 1999

Journal of Applied Physics

350

174

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An inductive technique for the measurement of dynamical magnetic processes in thin-film materials is described. The technique is demonstrated using 50 nm films of Permalloy (Ni 81 Fe 19). Data are presented for impulse-and step-response experiments with the applied field pulse oriented in the plane of the film and transverse to the anisotropy axis. Rotation times as short as 200 ps and free oscillations of the magnetization after excitation are clearly observed. The oscillation frequency increases as the dc bias field parallel to the anisotropy axis increases as predicted by classical gyromagnetic theory. The data are fitted to the Landau-Lifshitz equation, and damping parameters are determined as a function of dc bias field. Damping for both impulse and step excitations exhibits a strong dependence on bias field. Damping for step excitations is characterized by an anomalous transient damping which rapidly increases at low dc bias field. Transformation of the data to the frequency domain reveals a higher order precessional mode which is also preferentially excited at low dc bias fields. A possible source for both phenomena is precessional mode saturation for large peak rotations. The technique has the potential for 20 ps resolution, although only 120 ps resolution is demonstrated due to the limited bandwidth of the waveguides used.

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Section: Discussionmentioning

confidence: 99%

Inductive measurement of ultrafast magnetization dynamics in thin-film Permalloy

Silva

Lee

Crawford

et al. 1999

Journal of Applied Physics

350

174

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“…By applying a delay of 1 ns or multiples to the magnetizing pulse with respect to the SR pulses and by repeating the experiment the overall time resolution of about 1 ns is obtained ͑pump and probe mode͒. 7,8 In Fig. 2 we present the surface sensitive and bulk sensitive magnetization data as a function of time t after the application of an external field antiparallel to the previous saturated magnetization state (t 0 ).…”

mentioning

confidence: 99%

“…The spin polarization of the ejected electron beam SPϭ(I up ϪI down )/(I up ϩI down ), where I up(down) are the spin-up or -down intensities, was measured and independently registered after each pulse of synchrotron radiation, i.e., at 8.333 MHz rate. 7,8 The measure of the bulk magnetization reversal dynamics was obtained by means of an induction search coil in otherwise identical experimental and timing conditions. The external magnetic field was applied to the whole sample by means of a current pulse in a low inductance coil.…”

mentioning

confidence: 99%

Dynamics of surface magnetization on a nanosecond time scale

Sirotti

Girlando²,

Prieto

et al. 2000

Phys. Rev. B

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The dynamics of surface magnetization is measured with ns time resolution by spin-polarimetry of the total photoemission yield excited by synchrotron radiation pulses. The surface response is compared to the bulk magnetization dynamics as obtained by induction measurements. The surface and the bulk show distinct magnetization dynamics indicating weak coupling during the reversal process in the ns-s time domain. Ultrathin layers of Fe as well as three-layer Fe/Cu/Fe exchange coupled structures were grown on top of an amorphous soft-ferromagnetic substrate ͑Vitrovac͒ and showed different reversal dynamics.The surface of a ferromagnet has a special magnetic behavior with respect to the bulk. 1,2 The electronic structure of the surface layer implies that exchange is anisotropic, i.e., the exchange stiffness is different on a path within the layer compared to a path perpendicular to it. 3 The surface magnetization of the 3d ferromagnetic metals is characterized by enhanced spin and orbital magnetic moments with respect to the bulk. 4,5 The critical behavior of the magnetization near the Curie temperature (T C ) is described by surface critical exponents which differ from the bulk ones. The ferromagnetic/paramagnetic transition itself may occur at a different temperature with respect to the bulk T C . 6 Based on these considerations alone one expects the dynamics of magnetization and of magnetization reversal at a ferromagnetic surface to be different than in the bulk.Our experiments are based on the surface sensitivity of the measurement of spin polarization ͑SP͒ of the photoemission yield as excited by synchrotron radiation ͑SR͒ in the UV and soft x-ray energy range, and on the pulsed structure of the radiation from an undulator source on a positron storage ring. 500 ps-long pulses of SR at time intervals of 120 ns, were obtained exploiting the ''two bunch mode'' of the SuperAco storage ring at Orsay. The polychromatic undulator radiation or monochromatic radiation of energy hϭ200 eV from the undulator source DOMINO at SuperAco was focused to a spot of about 3ϫ1 mm and impinged on the sample surface. This sets the lateral scale of the experiment which is therefore representative of a macroscopic magnetic behavior of the surface, i.e., integrated over the domain structure. Atomically clean surfaces of a soft-magnetic ribbon, as well as iron monolayers or iron/copper/iron interfaces, were prepared by ion sputtering and e-beam evaporation techniques in an ultrahigh vacuum environment, and measured at room temperature. The primary and secondary photoejected electrons from the sample surface were collected by an electrostatic accelerator lens and directed to the thin Au target of a 100 KV Mott scattering detector. The spin polarization of the ejected electron beam SPϭ (I up

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“…Early spin-resolved studies focused on transitions taking place on ns to ps timescales [264][265][266][267]. More recently experiments have established that upon laser excitation, itinerant ferromagnets lose their longrange magnetic order within a few hundred fs [268][269][270][271].…”

Section: Dynamicsmentioning

confidence: 99%

Spin-Resolved Valence Photoemission

Seddon

2014

Handbook of Spintronics

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Spin-resolved valence photoemission has recently seen a resurgence of interest fostered by exciting results in a range of interesting materials. Reviewed here are the basics of, the instrumentation for, and techniques useful in spin-resolved photoemission, together with illustrative examples of its utilization for materials of general importance and of particular relevance to spintronics applications. The example materials are broadly classified into nonmagnetic and magnetic systems. The former covers Rashba systems and topological insulators. The latter includes thin films, half-metals, adsorbates and induced moments, and, finally, a short section on imaging. The review is not intended to be comprehensive in its coverage but rather to provide an introduction to hardware and techniques together with an overview of selected results and state-of-the-art developments. List of Abbreviations 1DOne

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Time-resolved surface magnetometry in the nanosecond scale using synchrotron radiation

Cited by 23 publications

References 17 publications

Inductive measurement of ultrafast magnetization dynamics in thin-film Permalloy

Inductive measurement of ultrafast magnetization dynamics in thin-film Permalloy

Dynamics of surface magnetization on a nanosecond time scale

Spin-Resolved Valence Photoemission

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