D. Hernandez, F. Rodriguez, M. Moreno and H. U. Güdel
Pressure dependence of the crystal field spectrum of the NH4MnCl3
perovskite: Correlation between 10Dq, Ne and Nt, and the Mn-Cl
distance in MnCl64- complexes
Physica B 265, 186-190 (1999)
Abstract:
This work investigates the pressure-dependence of the crystal field (CF)
spectrum of MnCl64- complexes in
NH4MnCl3. The aim is to determine the variation of 10Dq as
well as the bonding parameters Ne and Nt deduced from the absorption spectra,
with the Mn¯Cl distance. The selected crystal provides a perfect
Oh symmetry for Mn2+ allowing a direct correlation between
the pressure and the Mn¯Cl distance through the bulk modulus. Precise
values of the variations of the spectroscopic parameters with P were
obtained from the linear behaviour exhibited by the six single CF excitations in
the 0¯60 kbar range. It is worth pointing out that an
R-dependence of 10Dq on the basis of a KR–n
variation with n close to 7 was attained from the pressure-induced
shifts. A remarkable feature is the reduction of Ne and Nt upon pressure.
Although Ne < Nt due to the greater bonding character of the
eg-orbitals, its variation with pressure however is smaller than that
of the p-bonding
t2g-related Nt parameter.