We have found a photoinduced phase transition (PIPT) in the mixed-valence (MV) gold complex Cs2Au2Br6 from the MV state (ambient pressure phase) to the single-valence (SV) phase (high-pressure phase) in the presure region from 6.4to 6.8 Gpa. We have observed an accumulation effect of each pulse shot, and have ascribed it to stabilization of the photogenerated SV clusters due to the cooperative Jahn-Teller instability of Au2+ ions. The PIPT shows a distinct threshold behavior against the photon density as well as the shots number, which has been interpreted in terms of te critical nucleation of the photoinjected SV clusters. We further found that the phototransformed SV phase is not stable below 5.5 GPa. and changes into the former MV phase after a long dead time of～104s.

Dynamics of the spin system has been invesdtigated in a ferromagnetic La0.7 Ca0.3 MnO3 film by means of a time-resolved pump-probe method. In a weak excitation condition, the relaxation time T increases critically on approaching the critical temperature Tc (=262K) from the low-temperature side as Tx|T/Tc-1|-1.39 for T>200k. Surprisingly, the same scaling relation holds even after strong excitation in a much wider temperature range down to～10K. We will discuss these behaviors in terms of photoinduced growth of the charge-ordering fluctuations.

Photoexcitation effects on the spin states were investigated for a prototypical spin-crossover complex [Fe(ptz)6] (BF4)2 (ptz=1-propyltetrazole) by the pump and probe technique at 77K. We have found (I) superlinear increase of density nHs of the photoexcited high-spin molecules when the excitation power density P exceeded a critical value (=120mW/cm2) and (ii) optical hysteresis between the P-increasing and the P-decreasing runs. These characteristic features are well reproduced by the Monte Carlo simulation based on the Ising model, in which the spin state of the respective Fe2+ion is represented by the pseudospins.

Thermal diffusivity has been investigated in ordered double perovskite Sr2FeMoO6 measn of transient surface grating technique in te temperatue rage of 300-450K. The thermal diffusivity showas an apprecialve decrese form 39mm/2s at 300K to 37mm/2 at 360K in the ferromagnetic phase, and then steeply drops to 10mm2/s with furtherincreasing temperature above the critical temperature Tc～380K. Such an abrupt decrease of the thermal diffusivity has been ascribed to the structural phase transition at Tc. We further investigate the lattice effect on the thermal diffusivity in A2FeMoO6 (A=Ca, Sr and Ba) by substitution of CA2+or Ba2+ ions for Sr2+ions at 300K. We find that the thermal difusivity increases form 35mm2/s for A=Ca to 41mm2/s for A=Ba. Considering the change of the Fe-O-Mo bond angle and hence the wider one-electrom bandwidth W.