Elastic and Magnetic Dynamics of Nanomagnet-Ordered Arrays Impulsively Excited by Subpicosecond Laser Pulses

Abstract

This Letter reports on the first observation of elastic and magnetic dynamics of ordered arrays of permalloy nanodots excited by low-intensity 120 fs light pulses. The first order of the diffraction pattern, generated by the probe beam in a pump-probe configuration, is used for time-resolved reflectivity and time-resolved magneto-optical Kerr effect measurements. The nonadiabatical absorption of the pump triggers an acoustic standing wave, detected by the reflected probe signal, with a frequency related to the array wave vector. Instead, the magneto-optical signal exhibits, on the nanosecond time scale, the signature of the heat-exchange diffusion processes. In addition, a clear oscillation of the magnetic signal, at a frequency close to the frequency of the acoustic wave, is unambiguously detected. Finally, the interplay between the elastic and magnetic dynamics is analyzed and interpreted.

Three-dimensional shape dependence of spin-wave modes in single FePt nanomagnets

“…The film has a uniform thickness in the direction perpendicular to the substrate, but the curvature of thesphere's surface causes a radial change in the actual thickness from center to edge (Fig. 1b cartoon cross-section).Measuring the intrinsic magnetization dynamics free from dipolar effects and non-magnetic oscillation modes present in a close packed array [19][20][21] requires use of single magnetic elements.To isolate a spherical cap, sample areas that were sparsely populated with spheres were identified. Then, focused ion-beam milling was used to remove the surrounding magnetic film to an outer diameter of 6-8 μm, which is larger than our probe spot size.…”

Femtosecond laser-induced optical anisotropy in a two-dimensional lattice of magnetic dots

“…There are a number of papers in this field tackling the problems of magneto-optics [6][7][8], opto-acoustics [9,10], and plasmonics [11][12][13], often extending the experimental approaches into the nonlinear domain [14] or employing time-resolved techniques [15][16][17][18][19].…”

Thermomechanical behavior of surface acoustic waves in ordered arrays of nanodisks studied by near-infrared pump-probe diffraction experiments

“…To demonstrate that twodimensional surface acoustic waves (2DSAWs) can be excited in ordered arrays of metallic nanodisks, by sub-ps light pulses, the infrared diffraction time-resolved experiment reported in Ref. 7 is here further extended and improved. In the present work, by measuring the frequencies of the oscillations of the first order diffracted light, as a function of the array periodicity D, we demonstrate that two-dimensional SAWs, with a wavevector q defined by | q|=2π/| D|, can be excited by a near-infrared ultrashort laser pulse.…”

“…In a recent letter [7], focused on the study of the magnetic dynamics of ordered arrays of magnetic nanodisks on silicon, we suggested the possibility of triggering a collective acoustic excitation of the nano-disk array/silicon coupled system. To demonstrate that twodimensional surface acoustic waves (2DSAWs) can be excited in ordered arrays of metallic nanodisks, by sub-ps light pulses, the infrared diffraction time-resolved experiment reported in Ref.…”