EPR STUDIES OF THE HAMILTONIAN PARAMETERS OF THE SIMULTANEOUS
AXIAL AND ORTHORHOMBIC JAHN-TELLER SPECTRA OF Cu2+ IN Cd2(NH4)2(SO4)3
SINGLE CRYSTALS AT DIFFERENT TEMPERATURES
This paper presents the study of the effective Hamiltonian parameters (g1, g2,
A1, A2) and the observed g and A tensors of the derivative axial and orthorhombic Jahn-
Teller EPR spectra of Cu2+ in Cd2(NH4)2(SO4)3 single crystals at different temperatures. The
variations of these parameters with temperature in the three mutually perpendicular planes
of the crystal confirm axial symmetry for T>Tc and orthorhombic symmetry for T<Tc in this
system. The simultaneous axial and anisotropic symmetries of the spectra owe their origin to
the behaviour of Cu2+ ions in the three JT potential wells because they can undergo
reorientation from one well to another or quantum tunnelling among them which depends on
temperature, burial height or thickness and energy of the ions. The results show that the
components of the activation energy and Fermi-contact parameter increase with temperature
while the decrease of the anisotropy parameter (u) is more than it compensates for the slight
increase in the effective Hamiltonian parameters g1 and g2 with temperature
