Understanding the mechanism of spin switching in ferrimagnets via the excitation of THz pulses holds promise for future-generation magnetic memory devices. Such spin switching can be accomplished by the Zeeman torque exerted by the THz pulses on the magnetic spins. Theoretical and experimental works have established that the field derivative of a terahertz pulse also exerts a torque, field derivative torque (FDT). Here, we investigate the role of the FDT in the spin switching in ferrimagnetic ${\mathrm{Gd}}_{\frac{3}{2}}{\mathrm{Yb}}_{\frac{1}{2}}{\mathrm{BiFe}}_5{\mathrm{O}}_{12}$ using a computational approach. Our results foresee that the spin switching in the presence of the FDT requires less THz magnetic fields than the spin switching without the FDT. Without the FDT terms, the spin switching in the considered system requires an extremely high magnetic field. Furthermore, we compute the switching and nonswitching contour diagrams to show that the FDT tremendously enhances the possibility of spin switching. These results not only shed light on the significance of the FDT in magnetization switching but also suggest materials where the switching effect is pronounced.

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• Magnetization switching
• Spin torque
• Ferrimagnets
• Landau-Lifschitz-Gilbert equation