Thermally induced magnetization switching in Gd/Fe multilayers

A theoretical model of Gd/Fe multilayers is constructed using the atomistic spin dynamics formalism. By varying the thicknesses and number of layers we have shown that a strong dependence of the energy required for thermally induced magnetization switching (TIMS) is present; with a larger number of interfaces, lower energy is required. The results of the layer resolved dynamics show that the reversal process of the multilayered structures, similar to that of a GdFeCo alloy, is driven by the antiferromagnetic interaction between the transition-metal and rare-earth components. Finally, while the presence of the interface drives the reversal process, we show here that the switching process does not initiate at the surface but from the layers furthest from it, a departure from the alloy behavior which expands the classes of material types exhibiting TIMS.

Figure 1

Schematic of the Gd/Fe multilayered structures.

Figure 2

Numerically calculated magnetization curves of each sublattice for the Gd/Fe mulitlayers as a function of temperature. Results are shown for a range of the number of repeats of the layers.

Figure 3

(a) Time dependence of the electron and phonon temperature from the two-temperature model. (b) and (c) Ultrafast magnetization dynamics curves for the Fe (solid lines) and Gd sublattices (dashed lines) for a range of pump fluences for 32 repeats ($N=32$) at short delay time in panel (b) and at long delay time in panel (c). Note the three different time scales for the axes in panels (a), (b), and (c).

Figure 4

Numerically calculated the switching probability as a function of the laser energy for samples $N=8$, $N=16$, and $N=32$.

Figure 5

Switching times of both Fe sublattice and Gd sublattice as a function of the laser energy for samples $N=8$, $N=16$, and $N=32$.

Figure 6

Layer-resolved reversal times for each Fe and Gd plane in the $N=16$ structure. The direction of the arrows represent the direction away from the interface to the central plane. The numbers represent the plane index where 1st is the interface plane up to the central plane (2nd for Gd and 6th for Fe).