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Femtosecond optical reflectivity measurements of lattice-mediated spin repulsions in photoexcited LaCoO3 thin films

Johan Bielecki (Institutionen för teknisk fysik, Kondenserade materiens fysik) ; A. D. Rata ; Lars Börjesson (Institutionen för teknisk fysik, Kondenserade materiens fysik)
Physical Review B. Condensed Matter and Materials Physics (1098-0121). Vol. 89 (2014), 3, p. art. no. 035129.
[Artikel, refereegranskad vetenskaplig]

We present results on the temperature dependence of ultrafast electron and lattice dynamics, measured with pump-probe transient reflectivity experiments, of an epitaxially grown LaCoO3 thin film under tensile strain. Probing spin-polarized transitions into the antibonding e(g) band provides a measure of the low-spin fraction, both as a function of temperature and time after photoexcitation. It is observed that femtosecond laser pulses destabilize the constant low-spin fraction (similar to 63%-64%) in equilibrium into a thermally activated state, driven by a subpicosecond change in spin gap Delta. From the time evolution of the low-spin fraction, it is possible to disentangle the thermal and lattice contributions to the spin state. A lattice mediated spin repulsion, identified as the governing factor determining the equilibrium spin state in thin-film LaCoO3, is observed. These results suggests that time-resolved spectroscopy is a sensitive probe of the spin state in LaCoO3 thin films, with the potential to bring forward quantitative insight into the complicated interplay between structure and spin state in LaCoO3.


Denna post skapades 2014-08-21. Senast ändrad 2015-01-21.
CPL Pubid: 201764


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