Abstract
The time-resolved magnetooptical Kerr effect in the substrate-strain-induced insulating ferromagnetic phase in (Pr0.6Ca0.4)MnO3 thin films on two different substrates was measured in a magnetic field up to 1.1 T. The photoinduced Kerr rotation and ellipticity show remarkably different magnetic-field dependence. From the comparison of the magnetic-field dependences of the photoinduced and static Kerr rotation and ellipticity we conclude that a transient ferromagnetic metallic phase, embedded within the insulating ferromagnetic phase, is created upon the photoexcitation at low temperatures. A comparison of temporal dependence of the photoinduced Kerr signals with the photoinduced reflectivity indicates that the change of the fractions of the phases takes place on a timescale of ten picoseconds independent of the substrate.