Eur. Phys. J. B 10, 271-275 (1999)
https://doi.org/10.1007/s100510050855

Analytical solution of 1D Ising-like systems modified by weak long range interaction

Application to spin crossover compounds

¹ Laboratoire de Magnétisme et d'Optique (CNRS-URA 1531) , Université de Versailles, 78035 Versailles Cedex, France
² Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität Mainz, 55090 Mainz, Germany

Corresponding author: ^a spiering@iacgu7.chemie.uni-mainz.de

Received: 26 November 1998
Published online: 15 July 1999

Abstract

It is well-known that 1D systems with only nearest neighbour interaction exhibit no phase transition. It is shown that the presence of a small long range interaction treated by the mean field approximation in addition to strong nearest neighbour interaction gives rise to hysteresis curves of large width. This situation is believed to exist in spin crossover systems where by the deformation of the spin changing molecules, an elastic coupling leads to a long range interaction, and strong bonding between the molecules in a chain compound leads to large values for nearest neighbour interaction constants. For this interaction scheme an analytical solution has been derived and the interplay between these two types of interaction is discussed on the basis of experimental data of the chain compound which exhibits a very large hysteresis of 50 K above RT at 370 K. The width and shape of the hysteresis loop depend on the balance between long and short range interaction. For short range interaction energies much larger than the transition temperature the hysteresis width is determined by the long range interaction alone.