Connection between Reorientational Motions of NH_{3} Groups and Phase Transitions in [Ni(NH_{3})_{6}](NO_{3})_{2} and [Mg(NH_{3})_{6}](NO_{3})_{2} Compounds

• Authors: A. Migdał-Mikuli , E. Mikuli
• Languages of publication: EN

Abstracts

EN

Quasielastic neutron scattering data for [Νi(ΝH_{3})_{6}](ΝO_{3})_{2} and [Mg(ΝH_{3})_{6}](NO_{3})_{2} were subjected to a new analysis. On the basis of the excess of intensity of elastic component observed in these spectra in comparison to the intensity of this component resulting from the applied reorientational model this analysis determined temperature dependence of the new "R" parameter. This parameter gives us information concerning the number of these NH_{3} groups which in the [Me(NΗ_{3})_{6}]^{2+} cation reorientate with the correlation time of order of 10^{-12} s. It has been ascertained that in phases I and II of both substances under study all NH_{3} groups reorientate fast (R = 6ΝH_{3} groups), whereas in phases III and IV only part of these groups reorientate fast (R = 3ΝΗ_{3} groups - in the case of [Νi(ΝΗ_{3})_{6}](ΝO_{3})_{2} and R = 2ΝΗ_{3} groups - in the case of [Mg(ΝΗ_{3})_{6}](NO_{3})_{2}). Moreover, the temperature dependence of reorientational correlation time τ for these fast reorienting ΝH_{3} groups were also determined. The remaining NH_{3} groups reorientate on a much slower time scale. Both temperature dependencies: R vs. Τ and τ vs. Τ register a deep thermal hysteresis of the phase transition: phase II - phase III (Τ^{h}_{C2} - T^{c}_{C2} ≈ 95 K and ≈ 35 K respectively for [Ni(ΝΗ_{3})_{6}](ΝO_{3})_{2} and [Mg(ΝΗ_{3})_{6}](NO_{3})_{2}).

Keywords

EN

64.70.Kb; 28.20.Cz; 61.50.Ks; 35.20.Yh

• Publisher: Institute of Physics, Polish Academy of Sciences
• Journal: Acta Physica Polonica A
• Year: 1995
• Volume: 88
• Issue: 3
• Pages: 527-532

Dates

published

1995-09

received

1995-04-27

Contributors

author

A. Migdał-Mikuli

• Chemical Faculty of the Jagiellonian University, R. Ingardena 3, 30-060 Kraków, Poland

author

E. Mikuli

• Chemical Faculty of the Jagiellonian University, R. Ingardena 3, 30-060 Kraków, Poland