Fig. 2: Ultrafast magnetization of FeRh in FeRh/Cu heterostructure.
From: Spin current driven by ultrafast magnetization of FeRh
The dynamic Kerr rotation (ΔθK) by ultrafast magnetization of FeRh at (a) short timescale <10 ps (sub-ps and ps dynamics) and (b) long timescale <500 ps (sub-ns dynamics). The magnetization direction of the FM phase of FeRh is set by an external magnetic field of 0.15 T, which is along the out-of-plane direction. The left y-axis is the dynamic Kerr rotation, and the right y-axis is the relative magnetization (ΔM). ΔM is determined as \(\triangle M=\frac{\triangle {\theta }_{K}}{{\theta }_{K}}\div\frac{{M}_{z}}{{M}_{s}}\), where θK is the static Kerr rotation of 5.8 mrad for the saturation magnetization (Ms) of the FM phase of FeRh, and Mz is the z-component of magnetization. With an external field of 0.15 T, Mz/Ms is 0.13. The color indicates the pump fluence in a unit of J m−2: 0.9 (black square), 2.2 (red circles), 3.5 (blue up-triangles), 5.3 (green down-triangles), 7.1 (magenta diamonds), 8.8 (orange stars), 10.6 (purple left-triangles), and 16.4 (dark yellow right-triangles). In a, a major response occurs at 2~4 ps (ps dynamics). In addition, a subtle peak appears at 0.5 ps (sub-ps dynamics). A dashed straight line at the time zero indicate the position of the pump pulse. c The dynamic Kerr rotation by the ultrafast demagnetization of the FM phase of FeRh with a pump fluence of 7.1 J m−2 at a base temperature (Tb) of 430 K (red circles). As a reference, ultrafast magnetization at a base temperature of 300 K with the same pump fluence is shown as black squares. There is 2.5 ps time delay between the ultrafast demagnetization and ultrafast magnetization.
