Dynamics of spin and orbital phase transitions in YVO3.

YVO3 exhibits a well separated sequence of orbital and spin order transitions at 200 and 116 K, followed by a combined spin-orbital reorientation at 77 K. It is shown that the spin order can be destroyed by a sufficiently strong optical pulse within less than 4 ps. In contrast, the orbital reordering transition from C-type to G-type orbital order is slower than 100 ps and goes via an intermediate nonthermal phase.