Tracking picosecond strain pulses in heterostructures that exhibit giant magnetostriction

Abstract

We combine ultrafast X-ray diffraction (UXRD) and time-resolved Magneto-Optical Kerr Effect (MOKE) measurements to monitor the strain pulses in laser-excited TbFe 2 /Nb heterostructures. Spatial separation of the Nb detection layer from the laser excitation region allows for a background-free characterization of the laser-generated strain pulses. We clearly observe symmetric bipolar strain pulses if the excited TbFe 2 surface terminates the sample and a decomposition of the strain wavepacket into an asymmetric bipolar and a unipolar pulse, if a SiO 2 glass capping layer covers the excited TbFe 2 layer. The inverse magnetostriction of the temporally separated unipolar strain pulses in this sample leads to a MOKE signal that linearly depends on the strain pulse amplitude measured through UXRD. Linear chain model simulations accurately predict the timing and shape of UXRD and MOKE signals that are caused by the strain reflections from multiple interfaces in the heterostructure.

Heat Transport without Heating?—An Ultrafast X‐Ray Perspective into a Metal Heterostructure

“…[37] The spatiotemporal strain η(z, t) (Figure 3) is used to calculate the X-ray diffraction pattern by dynamical X-ray diffraction theory. [26,30,38] γ S (mJ cm −3 K −2 ) 0.74 [33] 0.10 [33] 1.06 [33] 0.38 [51] -C ph (J cm −3 K −1 ) 2.85 [52] 3.44 3.94 2.33 [51] 1.80 [53] κ 0 e (W m −1 K −1 ) 66 [54] 396 [33] 81 [33,55] 52 κ ph (W m −1 K −1 ) 5 [54] 5 9.6 [55] 5 1 [53] g (PW m −3 K −1 ) 400 [56] 63 [56] 360 [56] 100 - [53] v s (nm −1 ps) 4.2 [57,58] 5.2 [56,90] 6.3 [61] 4.2 5.7 [53] Γ e 2.4 [62] (0.9) 0.9 [62] (1.1) 2.0 [62] 1.3 [62] -Γ ph 3.0 [62] (2.5) 1.7 [62] (2.1) 1.65 [62] 1.5 [62] 0.3 [53] www.afm-journal.de www.advancedsciencenews.com…”

“…[ 37 ] The spatio‐temporal strain η( z , t ) ( Figure ) is used to calculate the X‐ray diffraction pattern by dynamical X‐ray diffraction theory. [ 26,30,38 ] The evaluation of the simulated Bragg peak shifts is plotted as continuous lines in Figures 1 and .…”

Measurement of transient strain induced by two-photon excitation

“…Consequently, a rectangular-shaped bipolar strain wave is launched upon NIR excitation and a semiexponential-shaped bipolar strain wave is launched upon NUV excitation [8]. The average strain in the Bi:YIG layer is shaped accordingly [52], which we monitor directly with UXRD [3,8,53]. The different intensity profiles also determine the deposition of heat.…”

Time-Resolved Imaging of Magnetoelastic Waves by the Cotton-Mouton Effect

“…Such a coupled wave is called a magnetoelastic wave [7,[15][16][17][18]. The propagation dynamics of magneto-elastic waves depends on the excitation mechanism driven by laser irradiation [19,20]. Here, the excitation mechanisms include impulsive stimulated Raman scattering (ISRS) [3], inverse Faraday effects (IFEs) [5,21,22], photoinduced demagnetization, and photoinduced change in the magnetic anisotropy [6,23].…”