Magnetic Domain Control of ErFeO₃ by Intense Terahertz Free Electron Laser Pulses

The control of magnetic domain in correlated spin systems by optical pulses has been gaining importance in spintronics and related fields. In particular, ultrafast control of magnetic domain is one of the top areas of interest. Herein we demonstrate the magnetic domain control in ErFeO3 single crystal, a weak ferromagnet, induced by high-intensity terahertz (THz) pulse excitation from a free-electron laser. THz pulses with a central frequency of 4 THz and pulse energy in the order of 10 mJ were used. The microscopic images of the magnetic domain inversion induced by the THz irradiation were recorded by the Faraday-rotation method using a He–Ne probe laser. The experimental results of the THz pulse irradiation at room temperature and at low temperature around the spin reorientation phase transition are presented. We show that the THz pulse excitation can expand the minor magnetic domain toward the direction of the THz beam spot. The magnetic domain inversion is caused by the combination of depinning of the magnetic domain due to local heating and the entropic force owing to the thermal gradient induced by THz irradiation.