  We report on terahertz emission from a single layer ferromagnet which
involves the generation of backflow nonthermal charge current from the
ferromagnet/dielectric interface by femtosecond laser excitation and subsequent
conversion of the charge current to a transverse transient charge current via
the anomalous Hall effect, thereby generating the THz radiation. The THz
emission can be either enhanced or suppressed, or even the polarity can be
reversed, by introducing a magnetization gradient in the thickness direction of
the ferromagnet. Unlike spintronic THz emitters reported previously, it does
not require additional non-magnetic layer or Rashba interface.
