title: Re-appearance of cooperativity in ultra-small spin-crossover [Fe(pz){Ni(CN)₄}] nanoparticles.
abstract: A reverse nanoemulsion technique was used for the elaboration of [Fe(pz){Ni(CN)4}] nanoparticles. Low-temperature micellar exchange made it possible to elaborate ultra-small nanoparticles with sizes down to 2 nm. When decreasing the size of the particles from 110 to 12 nm the spin transition shifts to lower temperatures, becomes gradual, and the hysteresis shrinks. On the other hand, a re-opening of the hysteresis was observed for smaller (2 nm) particles. A detailed (57)Fe Mössbauer spectroscopy analysis was used to correlate this unusual phenomenon to the modification of the stiffness of the nanoparticles thanks to the determination of their Debye temperature.
authors.affiliation: Laboratoire de Chimie de Coordination, CNRS UPR-8241 and Université de Toulouse; UPS, INP, 31077 Toulouse (France).
authors.forename: Haonan
authors.initials: H
authors.lastname: Peng
authors.forename: Simon
authors.initials: S
authors.lastname: Tricard
authors.forename: Gautier
authors.initials: G
authors.lastname: Félix
authors.forename: Gábor
authors.initials: G
authors.lastname: Molnár
authors.forename: William
authors.initials: W
authors.lastname: Nicolazzi
authors.forename: Lionel
authors.initials: L
authors.lastname: Salmon
authors.forename: Azzedine
authors.initials: A
authors.lastname: Bousseksou
keywords: Debye temperature; Mössbauer spectroscopy; nanoparticles; spin crossover; transition metals