Electron paramagnetic resonance (EPR) study of Cr3+ doped cesium tetrabromozincate (CTBZ) single crystal is done at room temperature. The hyperfine structure for Cr53 isotope is also obtained. Two magnetically inequivalent sites for Cr3+ are observed. The spin Hamiltonian parameters are evaluated as: D = 234×10-4cm-1, E = 69×10-4cm-1, g = 2.0104, A = 80×10-4 cm-1 for site I and D = 235×10-4 cm-1, E = 70×10-4cm-1, g = 2.0061, A = 82×10-4cm-1 for site II, respectively. The optical absorption spectra are recorded at room temperature. The energy values of different orbital levels are determined. The values of various parameters obtained are: B = 602 cm-1, C = 2504 cm-1, Dq = 1870 cm-1, h = 1.63 and k = 0.21, where B and C are Racah parameters, Dq is crystal field parameter, and h and k are nephelauxetic parameters, respectively. Theoretical zero-field splitting (ZFS) parameters for Cr3+ at two sites in CTBZ are evaluated using superposition model and microscopic spin Hamiltonian theory. The theoretical ZFS parameters are in good agreement with the experimental values
