THz Switching of Antiferromagnets and Ferrimagnets

Using analytical calculations as well as computer simulations, we show that antiferromagnets can be switched on a time scale of picoseconds using THz laser pulses only. This all-optically triggered switching mechanism rests on the coordinated dynamics of the two interacting sublattices with an inertial character. We calculate the resonance frequencies in the nonlinear regime, the orbits, and estimate the field strength required for switching analytically. Furthermore, we demonstrate that ferrimagnets can be switched similarly at their compensation point.

Figure 1

Excitation of an antiferromagnet with a ps magnetic field pulse. (a) $l_z$ shows inertial behavior. (b) Excitation triggers inertial switching. (c) Energies during switching process.

Figure 2

(a) Precession of the antiferromagnet during the excitation with a magnetic field $\mathbf{B}$. The lines represent orbits of sublattice magnetizations. (b) Precession in zero field for $E>2d_z$. (c) $E>2d_z$.

Figure 3

$l_z$ after excitation of NiO with an ultrashort magnetic field pulse of different duration and strength.

Figure 4

Switching of a ferrimagnet at $T_M$ with an ultrashort magnetic field pulse.