Pressure and temperature hysteresis in the spin-transition solid Fe(btr)(2)(NCS)(2)center dot H2O, pure and diluted in Ni matrix

The hysteresis loops of the spin transition crystalline powder Fe(btr)(2)(N CS)(2).H2O, pure or diluted in a Ni-homologue, have been recorded as a func tion of temperature and pressure. The phase diagrams in (p, T) axes have be en determined. Pressure hysteresis loops, at constant temperature, have bee n obtained. A pressure-induced structural change is inferred from the data of the pure compound. The possible thermal quenching of the high-pressure s tructural phase is evidenced. A relationship between the shapes of the temp erature and pressure loops is established. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.