Terahertz Optomagnetism: Nonlinear THz Excitation of GHz Spin Waves in Antiferromagnetic FeBO3

Abstract

A nearly single cycle intense terahertz (THz) pulse with peak electric and magnetic fields of 0.5 MV=cm and 0.16 T, respectively, excites both modes of spin resonances in the weak antiferromagnet FeBO 3 . The high frequency quasiantiferromagnetic mode is excited resonantly and its amplitude scales linearly with the strength of the THz magnetic field, whereas the low frequency quasiferromagnetic mode is excited via a nonlinear mechanism that scales quadratically with the strength of the THz electric field and can be regarded as a THz inverse Cotton-Mouton effect. THz optomagnetism is shown to be more energy efficient than similar effects reported previously for the near-infrared spectral range.

Far- and midinfrared excitation of large amplitude spin precession in the ferromagnetic semiconductor InMnAs

“…Similarly to the finding reported recently in Ref. [33], the strength of the effect of light on magnetism is more a function of the photon flux than the total energy deposited into the sample. Therefore, our finding opens up a new avenue in experimental and theoretical studies of ultrafast laser-induced magnetization dynamics.…”

THz-Scale Field-Induced Spin Dynamics in Ferrimagnetic Iron Garnets

“…Here, χ ⊥ ≡ M 2 =δ is a constant inversely proportional to the exchange constant and α is the Gilbert damping parameter. It can be seen that the large THz field derivative term γ _ h i appears as the dominant driving force in accordance with our understanding of how dynamical THz fields may excite antiferromagnetic magnons in antiferromagnets (where m → 0) by Zeeman interaction [18,39]. Moreover, each equation of motion contains a mutually orthogonal component of the field derivative _ h x;y .…”

“…Varying time retardation between the THz pump and optical probe pulse, timeresolved measurements were obtained by mapping probe polarization changes induced by the THz pulse using a balanced photodetector. The strength of the THz electric field in free space was calibrated using the Pockels effect in a thin (110)-oriented GaP crystal and yields a maximum peak strength of jE THz j ≈ 1 MV=cm, implying a peak magnetic field of 0.33 T [18]. The THz pulse waveform and the corresponding Fourier spectrum are shown in Fig.…”

Generation of strong-field spectrally tunable terahertz pulses

“…While optical light predominantly interacts with valence electrons, terahertz radiation, defined as the frequency region between 0.1 and 10 terahertz, allows direct and selective access to the numerous low-energy excitations including lattice vibrations, spin waves, molecular rotations, quantum states and the internal excitations of bound electron-hole pairs [1][2][3][4][5][6][7][8][9][10][11][12]. Recent advances in the available terahertz brightness also enable non-resonant control over matter where the terahertz stimulus acts as ultrafast excitation [13][14][15][16]. While the selective control requires narrowband terahertz radiation, the non-resonant excitation relies on intense single-cycle terahertz pulses carrying a (multi-) octave spanning spectrum.…”