Terahertz Time-Domain Observation of Spin Reorientation in OrthoferriteErFeO3through Magnetic Free Induction Decay

Abstract

Terahertz time domain spectroscopy was performed on orthoferrite ErFeO3. Through the emission from the two magnetic resonance modes, we succeeded in observing the spin reorientation transition. Depending on the orientation of the single crystal, the reorientation can be detected as either mode switching between the two modes or polarization change of the emission. This method enables picosecond resolved observation of the reorientation without disturbances such as electronic excitation and heating, and it is expected to open the doorway to observe ultrafast reorientation with the terahertz pulse.

Terahertz emission spectroscopy of laser-induced spin dynamics inTmFeO3andErFeO3orthoferrites

“…This suggests that excitation of the mode also relies on thermal heating near the spin-reorientation phase transition. Although the THz emission spectroscopy measurements clearly reveal that the mode is excited in both TmFeO 3 and ErFeO 3 , it has never been observed before in either optical pump-probe measurements [10][11][12] or in timedomain THz absorption spectroscopy [25]. The appearance of this formerly unobserved spectral peak would suggest that the laser-induced spin dynamics of the orthoferrites may be more complicated than previously thought [43].…”

“…By analyzing absorption peaks in the normalized Fourier spectra of the pulses transmitted through the sample, one can obtain information about the spectrum of THz excitations in the sample. The details of the time-domain THz spectroscopy setup can be found elsewhere [22][23][24][25][26][27]. We analyze the THz transmission through the sample in terms of the normalized loss function σ (ω), defined as…”

“…It has been demonstrated that broadband pulses of THz radiation can serve as a probe of spin resonances in YFeO 3 [22][23][24], ErFeO 3 [25], NdFeO 3 [26], and Tb 3 Ga 5 O 12 [27]. A promising approach to control magnetic order with the help of intense-enough THz pulses has been suggested for NiO [28].…”

Ground state and magnetic phase transitions of orthoferriteDyFeO3

“…The rare-earth-based orthoferrites RFeO 3 have received a lot of research interests in last several decades, particularly in the manifestations of the spin structures and spin re-orientations. [15][16][17][18][19] In DyFeO 3 , the Fe 3+ moments exhibit G x A y F z (Fe I ) spin configuration in Bertaut's notation 20 at room temperature, that is, the main component of the magnetic moment is along the a axis, accompanying with weak ferromagnetism (WFM) along the c axis. 21,22 Upon lowering temperature, the Fe 3+ spins undergo a Morin transition 23 at T M = 50 K. At this transition the spin configuration changes to A x G y C z (Fe II ).…”

Magnetic field induced discontinuous spin reorientation in ErFeO3 single crystal

“…3,18,19 In order to uncover the mechanism of this process, the spin dynamics have been investigated by several kinds of technological methods, including terahertz time domain spectroscopy, ultrafast laser pulses, neutron diffraction, etc. [19][20][21] In AC measurements, an oscillating component is added to the static magnetic field, causing a time-dependent moment in the sample, which is a very sensitive probe for detecting a magnetic phase transition initiated by a change in the magnetocrystalline anisotropy energy. 22 The spin reorientation process in ErFeO 3 that spontaneously occurs at low temperature has been previously determined to be a continuous and coherent rotation of Fe 3þ .…”