Fig. 2: The 4f magnetization dynamics probed in diffraction.
From: Exchange scaling of ultrafast angular momentum transfer in 4f antiferromagnets
a, Sketch of the experimental scheme, with the scattering vector parallel to the sample’s [001] crystal direction and the two pulses arriving collinearly. The graph on top shows reciprocal space scans of the (001) magnetic reflection before excitation (bright) and 100 ps after excitation (dark) using an absorbed fluence of F = 0.24 mJ cm−2 (F/FC = 2.6). r.l.u. are reciprocal lattice units. b,c, Pump-induced changes in the antiferromagnetically ordered 4f moment for Ln = Sm and Tb, respectively, representing data from both light and heavy lanthanides, highlighting the large difference in timescales and fluences. Different curves (in differently shaded color) correspond to different pump fluences: from F/FC = 0.38 to 1.9 for Sm (0.05 to 0.28 mJ cm−2) and from F/FC = 0.32 to 3.2 for Tb (0.26 to 2.6 mJ cm−2). d, Total demagnetization amplitude as a function of normalized fluence for all materials (Methods; line is a guide for the eye). e, Exponential time constant of the dominant (slower) drop as a function of normalized fluence. The data are normalized to τC, the value at FC (inset). τC values are extracted for each compound from the best fit between all shown data and the relation \(\tau /\tau _{\mathrm{C}} = \sqrt {F/F_{\mathrm{C}}}\) (grey curve; Supplementary Section 5). Errors are defined in the Methods section.
