| In this work, we perform the first time-resolved Kerr measurements on the colossally magnetoresistive manganites, Pr0.67Ca0.33MnO 3 and La0.7Ca0.3MnO3. We find that Kerr spectroscopy reveals surface magnetic dynamics undetected by previously established techniques based on optical spectral weight transfer. These previously unobserved dynamics include photoinduced demagnetization of minority phase ferromagnetism and the first evidence for transient photonucleated magnetization in a manganite. Using independent yet simultaneous probes, we compare spin and charge dynamics and find that the dynamical connection between these two systems in the manganites may be weaker than previously thought. Our measurements also reveal that time-resolved Kerr spectroscopy can be a sensitive probe of phase-separation in these systems.; In Pr0.67Ca0.33MnO3, the hysteresis of the insulator-metal transition permits comparisons of insulating and metallic state non-equilibrium dynamics at the same temperature and magnetic field. We also employ supercontinuum white light generation to probe dynamic spectral weight transfer with greater than 1 eV bandwidth and subpicosecond time-resolution. These data are used to evaluate proposals that charge dynamics alone (witnessed through time-resolved reflectivity) can be used to measure spin-disordering rates in the manganites. Important differences between these systems and conventional ferromagnetic metals manifest as long-lived, magneto-optical coupling transients, which may be generic to all manganites.; In La0.7Ca0.3MnO3, time-resolved Kerr spectroscopy reveals the first evidence for transient photoinduced magnetization (PIM) near Tc. For temperatures above Tc, the PIM signature reaches full strength at the field-driven magnetic phase transition, while below Tc it exhibits a magnetic activation threshold of ∼0.5 T. We compare the temperature dependence of the effect with diffuse spin scattering and correlated polaron scattering previously measured with neutrons and discuss these findings in the context of phase-separation near Tc. |
