Methods and devices having means for writing storing and erasing which comprise an active medium containing at least one spin-transition parent compound

摘要

A chemical composition is provided for the manufacture of devices for storing and/or displaying information, comprising a network having a molecule which is formed from a metallic element Fe_(II) which is bonded to a 1-2-4 triazole ligand (H-Trz), which molecule further comprises one or more than one anions A selected from BF₄^−, ClO₄^−, CO₃^2−, Br^−, Cl^−, in accordance with the formulation:; $PTEXTPDATFe/PDATHILSBPDATII/PDAT/SB/HILPDAT(H-Trz)/PDATHILSBPDAT3/PDAT/SB/HILPDATA/PDATHILSBPDAT2/PDAT/SB/HILPDAT,/PDAT/PTEXT$ ;characterized in that this composition is used in the pure state in either one of the two crystalline phases (&agr;,&bgr;) at least one of which, referred to as the second phase (&bgr;), can be thermally induced on the basis of the other phase, referred to as the first phase (&agr;), at a temperature which is equal to or higher than a first reference temperature (To), which phases each show thermally inducible spin transitions between a low-spin state at a low first temperature (T_&agr;1, T_&bgr;1) and a high-spin state at a high second temperature (T_&agr;2, T_&bgr;2), the spin transitions which are associated with each phase being accompanied by a similar abrupt change in color of the compound and taking place in accordance with hysteresis cycles at different temperatures of the two phases, wherein the hysteresis cycle (T_&agr;1, T_&bgr;2) associated with the first phase (&agr;) occurs at a temperature which is higher than a second reference temperature (T_R), and the hysteresis cycle (T_&bgr;1, T_&bgr;2) associated with the second phase (&agr;) occurs at a temperature below the second reference temperature (T_R), the first reference temperature (To) being higher than the second reference temperature (T_R) and the highest spin-transition temperature (T_&agr;2).