Jahn-Teller EPA spectra of Cu2 + in MgSif6.6H20
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American Institute of Physics
Abstract
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The 34 GHz EPR spectrum ofCu2+ in MgSiF6-6H20 showed a "static" Jahn-Teller effect at 4.2
K with two inequivalent Jahn- Teller sites per unit cell. The six axially symmetric sets of Cu2+
lines had their z axes parallel to the three tetragonal axes of two cubes, which were rotated by
approximately 40" with respect to each other about a common (Ill) axis, which is the crystal c
axis. The measured spin-Hamiltonian parameters at 4.2 K for each set of lines were
g11 = 2.47 ± 0.01, g1 = 2.10 ± 0.01 , and lA 11 1 = (110 ± 3)X 10- 4 em- •. There was a gradual
decrease in the anisotropy of the spectrum on warming the crystal, with a single, nearly isotropic
line being observed above 220 K. At 270 K the spectrum had axial symmetry about the c axis with
Kn = 2.23 ± 0.01 and g~ = 2.25 ± 0.01 . The temperature evolution of the spectrum was
interpreted in terms of a Boltzmann distribution over inequivalent distorted Jahn-Teller
configurations, with one potential well lowered by an amount L1:::::: I 05 em- 1 below the other two.
Keywords
QC Physics