Investigation of ultrafast demagnetization and cubic optical nonlinearity of Ni in the polar geometry

Wilks, Richard J.; Hicken, R. J.; Ali, M.; Hickey, B. J.; Buchanan, James D. R.; Pym, A. T. G.; Tanner, B. K.

doi:10.1063/1.1687538

Cited by 37 publications

(35 citation statements)

References 10 publications

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“…Second, ͑b͒ via the inverse Faraday effect, a coherent magnetization ͑parallel to the wave vector͒ is generated in the excited state. Such a coherent magnetization can be probed itself, 14 as will be discussed later in this paper. However, in this scenario, the magnitude of the magnetization vector is left behind unchanged after coherent effects are over.…”

Section: Influence Of Photon Angular Momentum On Ultrafast Demagnetizmentioning

confidence: 99%

“…On the other hand, it has been known for some years that pump polarization does not have a major influence in the spin response to laser excitation in transition metals. [12][13][14][15] The sample under investigation consists of a 10 nm thick Ni film sputtered on a SiO substrate and capped with 2 nm of copper to prevent from oxidation. The thickness of the ferromagnet has been especially chosen to match the light penetration depth ͑ϳ15 nm for Ni at a wavelength of 785 nm͒ in order to uniformly heat up the film throughout its thickness.…”

Section: Influence Of Photon Angular Momentum On Ultrafast Demagnetizmentioning

confidence: 99%

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Influence of photon angular momentum on ultrafast demagnetization in nickel

et al. 2007

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The role of photon angular momentum in laser-induced demagnetization of Nickel thin films is investigated by means of pump-probe time-resolved magneto-optical Kerr effect in the polar geometry. The recorded data display a strong dependency on pump helicity during pump-probe temporal overlap, which is shown to be of non-magnetic origin. By accurately fitting the demagnetization curves we also show that demagnetization time τM and electron-phonon equilibration time τE are not affected by pump-helicity. Thereby our results do not support direct transfer of angular momentum between photons and spins to be relevant for the demagnetization process. This suggests, in agreement with the microscopic model that we recently presented, that the source of angular momentum could be phonons or impurities rather than laser photons as required in the microscopic model proposed by Zhang and Hübner.

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Section: Influence Of Photon Angular Momentum On Ultrafast Demagnetizmentioning

confidence: 99%

Section: Influence Of Photon Angular Momentum On Ultrafast Demagnetizmentioning

confidence: 99%

Influence of photon angular momentum on ultrafast demagnetization in nickel

et al. 2007

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“…The laser beam profiler was also used to overlap the pump and probe spots before being removed so that the sample could be placed in the focal plane and between the pole pieces of an electromagnet. Two different electromagnets, 54,55 designed for optimal optical access, were used to apply a magnetic field either perpendicular to (polar magnet) or in the plane of (longitudinal magnet) the sample. The polar (longitudinal) electromagnets could deliver maximum fields of about ±11 kG ( ±4 kG) and allowed the angle of incidence of the probe to be set to 9…”

Section: Details Of the Experiments And Micromagnetic Simulation Pmentioning

confidence: 99%

Static and dynamic magnetic properties of densely packed magnetic nanowire arrays

et al. 2013

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The static and dynamic magnetic properties of magnetic nanowire arrays with high packing density (>0.4) and wire diameter much greater than the exchange length have been studied by static and time-resolved magneto-optical Kerr effect measurements and micromagnetic simulations. The nanowires were formed by electrodeposition within a nanoporous template such that their symmetry axes lay normal to the plane of the substrate. A quantitative and systematic investigation has been made of the static and dynamic properties of the array, which lie between the limiting cases of a single wire and a continuous ferromagnetic thin film. In particular, the competition between anisotropies associated with the shape of the individual nanowires and that of the array as a whole has been studied. Measured and simulated hysteresis loops are largely anhysteretic with zero remanence, and the micromagnetic configuration is such that the net magnetization vanishes in directions orthogonal to the applied field. Simulations of the remanent state reveal antiferromagnetic alignment of the magnetization in adjacent nanowires and the formation of vortex flux closure structures at the ends of each nanowire. The excitation spectra obtained from experiment and micromagnetic simulations are in qualitative agreement for magnetic fields applied both parallel and perpendicular to the axes of the nanowires. For the field parallel to the nanowire axes, there is also good quantitative agreement between experiment and simulation. The resonant frequencies are initially found to decrease as the applied field is increased from remanence. This is the result of a change of mode profile within the plane of the array from nonuniform to uniform as the ground state evolves with increasing applied field. Quantitative differences between experimental and simulated spectra are observed when the field is applied perpendicular to the nanowire axes. The dependence of the magnetic excitation spectra upon the array packing density is explored, and dispersion curves for spin waves propagating within the array parallel to the nanowire axis are presented. Finally, a tunneling of end modes through the middle region of the nanowires was observed. The tunneling is more efficient for wires forming densely packed arrays, as a result of the extended penetration of the dynamic demagnetizing fields into the middle of the wires and due to the lowering of the tunneling barrier by the static demagnetizing field of the array.

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“…This dual chopping scheme was found to give similar signal quality to the single pump chopping used in previous studies. 10,11 It also allowed the demagnetization to be observed directly on an oscilloscope connected to the output of the high-pass filter on the front end of the lock-in amplifier. The time delay was set using a translation stage with a stepper motor and encoder resolution of 0.1 µm.…”

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confidence: 99%

“…Optical pump-probe measurements were performed with pulses of 785 nm wavelength and 100 fs pulse width from a Ti:sapphire laser 10 at an 80 MHz repetition rate. Both pump and probe were focused to a spot with a diameter of 15 µm, which was limited by the beam divergence, and then carefully overlapped.…”

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confidence: 99%

Ultrafast demagnetization of Co25Ni75∕Pt multilayers with perpendicular anisotropy at elevated temperatures

Wilks

Hicken

Ali

et al. 2005

Journal of Applied Physics

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Ultrafast demagnetization has been studied in Si∕Pt(160Å)∕[Co25Ni75(x)∕Pt(8Å)]20 (x=3, 4.5, and 6 Å) multilayers with perpendicular anisotropy by magneto-optical pump-probe measurements in the polar geometry. Time-resolved measurements made in the saturated state showed that maximum demagnetization was achieved within 300 fs. Hysteresis loops were measured at a time delay of 1.3 ps for temperatures from 20 to 300 °C. The Curie temperature was found to increase from 150 to 250 °C with increasing Co25Ni75 thickness. By comparing the loops obtained with and without pump excitation, the increase in electron temperature due to the pump was estimated to be about 60 K.

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Investigation of ultrafast demagnetization and cubic optical nonlinearity of Ni in the polar geometry

Cited by 37 publications

References 10 publications

Influence of photon angular momentum on ultrafast demagnetization in nickel

Influence of photon angular momentum on ultrafast demagnetization in nickel

Static and dynamic magnetic properties of densely packed magnetic nanowire arrays

Ultrafast demagnetization of Co25Ni75∕Pt multilayers with perpendicular anisotropy at elevated temperatures

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