Terahertz Technology: Abstract-Terahertz emission spectroscopy of laser-induced spin dynamics in TmFeO3 and ErFeO3 orthoferrites

R. V. Mikhaylovskiy, E. Hendry, V. V. Kruglyak, R. V. Pisarev, Th. Rasing, and A. V. Kimel
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.90.184405

Using the examples of laser-induced spin-reorientation phase transitions in

TmFeO3 and

ErFeO3 orthoferrites, we demonstrate that terahertz emission spectroscopy can obtain novel information about ultrafast laser-induced spin dynamics, which is not accessible by more common all-optical methods. The power of the method is evidenced by the fact that, in addition to the expected quasi-ferromagnetic and quasi-antiferromagnetic modes of the iron sublattices, terahertz emission spectroscopy enables detection of a resonance optically excited at an unexpected frequency of ∼0.3–0.35 THz. By recording how the amplitude and phase of the excited oscillations depend on temperature and applied magnetic field, we show that the unexpected mode has all the features of a spin resonance of the

Fe3+ ions. We suggest that it can be assigned to transitions between the multiplet sublevels of the

6A1 ground state of the

Fe+3ions occupying rare-earth positions.

DOI: http://dx.doi.org/10.1103/PhysRevB.90.184405