TY - JOUR AU - Jeftic, Jelena AU - Varret, François AU - Hauser, Andreas AU - Roubeau, Olivier AU - Matsarski, Marie AU - Rivera, Jean-Pierre TI - Patterns during photoexcitation and high-spin -> low-spin relaxation in [Fe(Ptz)6](BF4)2 spin transition crystal PY - 1999 JF - Molecular Crystals and Liquid Crystals JA - Mol. Cryst. Liq. Cryst. SN - 1542-1406 VL - 335 SP - 511 EP - 520 L1 - http://www.informaworld.com/smpp/ftinterface~db=all~content=a757168909~fulltext=713240930 L3 - http://www.informaworld.com/smpp/content~db=all~content=a757168909 M3 - 10.1080/10587259908028892 UR - http://dx.doi.org/10.1080/10587259908028892 KW - spin transition KW - photography KW - laser photoexcitation KW - instability N2 - The propagation of the high-spin (HS) → low-spin (LS) relaxation at 53 K in a single crystal of the iron (II) spin-crossover compound [Fe(ptz)6](BF4)2 was followed by photography, after inducing the local photoexcitation to the metastable HS state at 20 K using the single wavelength (457 nm Ar± ion laser) irradiation. The photoinduced formation of the HS—LS patterns with a characteristic diameter of some 0.1 mm was observed to occur inhomogeneously at a macroscopic scale already during photoexcitation. The contrast between the HS (transparent) and the LS (purple) regions was amplified during relaxation. The effect is described in terms of a transient instability, for which a microscopic model in the mean-field approximation is proposed. The mechanism for the development of patterns at the macroscopic scale is discussed. ID - 494 ER -