Role of surface vibrational properties on cooperative phenomena in spin-crossover nanomaterials

Mirko Mikolasek (1) , Gautier Félix (1) , Gábor Molnár (1) , Ferial Terki (2) , William Nicolazzi (1) , Azzedine Bousseksou (1)

1 LCC - Laboratoire de chimie de coordination
2 ICGM ICMMM - Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier

The influence of surface/interface on the lattice dynamics of spin crossover nanoparticles has been investigated by a spring-ball model solved by Monte Carlo methods. The bond cohesion energy of the model has been extracted from Mössbauer spectroscopy measurements performed on the model compound Ni3[Fe(CN)6]. We show that the coupling between bulk and surface vibrational properties, which drastically affects the mechanical properties of the whole particle below a characteristic size, has a major impact on the phase stability of the particles. In the case of free surfaces, the Debye temperature decreases with the size and the first-order nature of the spin transition disappears. On the other hand, a hardening of the surface bonds leads to increasing particle stiffness with the size reduction. In this case, a persistence of the hysteretic behavior in the spin transition curve is also predicted in good agreement with previous theoretical and experimental results.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Mirko Mikolasek, Gautier Félix, Gábor Molnár, Ferial Terki, William Nicolazzi, et al.. Role of surface vibrational properties on cooperative phenomena in spin-crossover nanomaterials. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2014, 90 (7), pp.075402. ⟨10.1103/PhysRevB.90.075402⟩. ⟨hal-01203655⟩