Investigations on the Spin-Hamiltonian Parameters and Local Structure of the Orthorhombic Cu2+ Center in PbTiO3 Crystal

Li Chao-Ying, Cheng Li-Bin and Zheng Xue-Mei School of Physics and Electronic Information, Shangrao Normal University, Shangrao Jiangxi 334000, P.R. China

Received: September 14, 2014; In final form: March 11, 2015

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The spin-Hamiltonian parameters (the g factors gi and the hyperfine structure constants Ai, i = x, y, z) and local structure of the Cu2+ center in PbTiO3 are theoretically studied by using the perturbation formulae of these parameters for a 3d9 ion in an orthorhombically elongated octahedra. The orthorhombic center is attributed to Cu2+ occupying the host Ti4+ site associated with a nearest-neighbouring oxygen vacancy VO along the c-axis, and the impurity Cu2+ off-center displacement ΔZL (≈0.18 Å) is smaller than that of the host Ti4+ site (ΔZH ≈0.3 Å). Meanwhile, the planar Cu2+-O2- bonds are found to experience the relative variation ΔR (≈ 0.098 Å) along the a- and b-axes, respectively, due to the Jahn-Teller effect and the size mismatching substitution of Ti4+ by Cu2+. The theoretical spin-Hamiltonian parameters based on the above defect structure agree well with the observed values.

DOI: 10.12693/APhysPolA.127.1671 PACS numbers: 76.30.Fc, 75.10.Dg, 71.70.Ch