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

J.B Yerima¹, A.B Dikko^*1 and D.K De²

¹Department of Physics, Modibbo Adama University of Technology Yola, Nigeria.

²Department of Physics, Kaduna State University, Kaduna State, Nigeria.

 E-mail: abdikkozabi@gmail.com ABSTRACT: 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>T_c and orthorhombic symmetry for T<T_c 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