The role of ultrafast magnon generation in the magnetization dynamics of rare-earth metals

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Science Advances  23 Sep 2020:
Vol. 6, no. 39, eabb1601
DOI: 10.1126/sciadv.abb1601
  • Fig. 1 Comparison of 5d6s and 4f spin dynamics in Gadolinium and Terbium.

    Upper panels: Orbital-resolved spin model. The yellow arrows represent the energy flow from the laser-excited electrons into the lattice (Gep) and to the 5d and 4f spin systems. Note the different 4f spin–to–lattice couplings α4f in (A) Tb (J = L + S = 6, L = 3) and (B) Gd (J = S = 7/2, L = 0). In contrast, inter- and intra-atomic exchange constants (Jij and Jintra) are of comparable magnitude. Lower panels: Illustration of 5d6s and 4f spin dynamics about 1 ps after laser excitation. While in (B), the 4f spins (yellow arrows) are strongly excited by lattice motions and tilted with respect to Mz, in (A), they remain cold and aligned along the magnetization direction Mz. The 5d6s spins (red arrows) are additionally coupled to the optically excited valence electrons α5d and thus quiver around the 4f moments.

  • Fig. 2 Valence band photoemission spectra and MLD of Tb at 90 K.

    ARPES spectra probed with p-polarized light for opposite in-plane magnetization directions (red and blue, see inset) at normal emission ϑ = 0. The gray backfilled difference spectrum highlights the MLD, which was evaluated for the 8S7/2 spin component. The binding energy of minority (↓) and majority (↑) spin 5d valence bands (VB) and the exchange splitting were extracted at ϑ = 8 (see text).

  • Fig. 3 Magnetization dynamics of itinerant 5d and localized 4f moments in the rare earth metals Gd and Tb.

    The upper panels show the response of the 5d valence band exchange splitting, and the lower panels show the transient MLD of the 4f level for (A) Gd and (B) Tb, respectively. Error bars on the last data points show 2 SDs. The solid lines result from our orbital-resolved spin dynamics simulations using ab initio input parameters for Jij and Jintra. In the lower panels, the calculated reduced magnetization is shown. In the upper panels, the calculated dynamics of 5d magnetic moments is converted into the transient exchange splitting via first principles calculations (see the Supplementary Materials).

Supplementary Materials

  • Supplementary Materials

    The role of ultrafast magnon generation in the magnetization dynamics of rare-earth metals

    B. Frietsch, A. Donges, R. Carley, M. Teichmann, J. Bowlan, K. Döbrich, K. Carva, D. Legut, P. M. Oppeneer, U. Nowak, M. Weinelt

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    • Sections S1 and S2
    • Figs. S1 to S10

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