Spin-transition parent compounds and devices having means for writing, storing and erasing, which comprise an active medium containing at least one of said compounds

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.sub.(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 BF.sub.4. sup.-, ClO. sub.4.sup.-, CO.sub.3.sup.2-, Br.sup.-, Cl.sup.-, in accordance with the formulation:PPFe.sub.II (H-Trz).sub.3 A.sub.2,P P 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. sub.&agr;1, T.sub.&bgr;1) and a high-spin state at a high second temperature (T.sub.&agr;2, T.sub.&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.sub.&agr;1, T.sub.&agr;2) associated with the first phase (&agr;) occurs at a temperature which is higher than a second reference temperature (T.sub.R), and the hysteresis cycle (T.sub.. beta.1, T.sub.&bgr;2) associated with the second phase (&bgr;) occurs at a temperature below the second reference temperature (T.sub.R), the first reference temperature (To) being higher than the second reference temperature (T.sub.R) and the highest spin- transition temperature (T.sub. &agr;2).