Terahertz radiation from magnetoresistive   Pr$_{\text{0.7}}$Ca$_{\text{0.3}}$MnO$_{\text3}$ thin films
  Terahertz (THz) radiation with its spectrum extending up to 1 THz has been observed by an illumination of femtosecond optical pulses to optical switching devices fabricated on magnetoresistive manganite thin films; Pr$_{0.7}$Ca$_{0.3}$MnO$_3$. The THz radiation strongly depends on temperature $T$ and its $T$ trend reverses sign across charge-orbital and spin ordering $T$'s. 
N. Kida and M. Tonouchi