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Transient quantum isolation and critical behavior in the magnetization dynamics of half-metallic manganites

by Anne-Marie - published on

In an international collaboration between groups from Italy, Germany, Japan, France and Great Britain, we combine time resolved pump-probe Magneto-Optical Kerr Effect and Photoelectron Spectroscopy experiments supported by theoretical analysis to determine the relaxation dynamics of delocalized electrons in half-metallic ferromagnetic manganite La1-xSrxMnO3. We observe that the half-metallic character of La1-xSrxMnO3 determines the timescale of both the electronic phase transition and the quenching of magnetization, revealing a quantum isolation of the spin system in double exchange ferromagnets extending up to hundreds of picoseconds. We demonstrate the use of time-resolved hard X-ray photoelectron spectroscopy (TR-HAXPES) as a unique tool to single out the evolution of strongly correlated electronic states across a second-order phase transition in a complex material.

Physical Review B 100,045118

Time trace of the low binding energy structure evolution in Mn2p3/2 core level photoemission spectrum. Each point in the graph (filled squares with error bar) corresponds to the area of the difference between the no-pump spectrum and the spectrum recorded at a fixed pump-probe delay, in the range of energies 640.5-638 eV. To calculate the relative variation, it is divided by the area of the no-pump spectrum in the same range. Spectra in the case of -100ps, +100 ps and 3.1 ns are shown in top panels, with fitted intensities of the satellites. Blue lines are guides to the eye and the vertical error bars are obtained by the integral of the difference between no-pump and the most negative delays: the absolute value of their deviation from zero gives an estimate of the uncertainty on the integrals due to the measurement noise. The horizontal uncertainty is given by the probe pulse duration of 50 ps and is smaller than the symbol size. In the bottom: Sketch of the pump-probe HAXPES setup, with main values of the pump-probe scheme and geometric parameters.