The cooperative spin transition in [FexZn1-x(ptz)(6)](BF4)(2) .1. Elastic properties - An oriented sample rotation study by Brillouin spectroscopy

The complete set of seven elastic constants of the Fe(II) spincrossover compound [Fe(ptz)(6)] (BF4)(2) (ptz = 1-propyltetrazole) with crystal symmetry R3i was measured by Brillouin spectroscopy at 300 K. The measurement on the plate-like single crystals were performed using an oriented sample rotation technique and the combination of two scattering geometries. For comparison the elastic constants of two isostructural compounds were also measured at 300 K: the analogous perchlorate spincrossover compound [Fe(ptz)(6)] (ClO4)(2) and the zinc complex [Zn(ptz)(6)] (BF4)(2). The knowledge of the elastic constants is necessary for the calculation of the elastic interaction between the spincrossover molecules, and this is the first time that the complete set of elastic constants of a spincrossover compound has been measured directly.