INVESTIGATIONS ON THE EPR g FACTORS FOR THE SIX-COORDIANTED Cu²⁺(1) SITE IN YBa₂Cu₃O_6+x

Abstract

The EPR g factors g // and g ⊥ for the six-coordinated Cu 2+(1) site in YBa 2 Cu 3 O 6+x are theoretically investigated from the perturbation formulas for a 3 d 9 ion in tetragonally elongated octahedra. The related tetragonal crystal-field parameters Ds and Dt are determined from the superposition model and the structural data for the Cu 2+(1) site, by considering the effective elongation of the oxygen octahedron due to the Jahn-Teller effect of the Cu 2+ cluster. Based on the calculations, the effective elongation (≈ 15%) of the ligand octahedron is obtained for the signals at 100K. As for the EPR signals at room temperature, the elongation declines to merely 4%, corresponding to the smaller anisotropy Δ g (= g // - g ⊥). The theoretical results for the g factors are in good agreement with the observed values, and the local tetragonal distortion due to the Jahn-Teller effect is discussed.

Investigations on the local structure and spin Hamiltonian parameters for the orthorhombic Cu2+ center in Ca(OD)2

“…Fortunately, although the studied Cu 2+ center in Ca(OD) 2 shows some covalency (characterized by the covalency factor N ≈ 0.82), the spin-orbit coupling coefficient (≈151 cm -1 [27]) of oxygen in the OD -ligand is much smaller than that (≈829 cm -1 [23]) of the Cu 2+ impurity. Thus, the ligand contributions to the spin Hamiltonian parameters are expected to be very small and reasonably ignored for simplicity here, as treated in various works for some Cu 2+ centers in oxides [28,29]. Third, the errors in the local structure and the spin Hamiltonian parameters also arise from the approximation of the relationship 2 ( ) A R ≈ 9 4 ( ) A R [18][19][20], which would somewhat affect the orthorhombic field parameters (Eq.…”

New Modular Organic Platform for Understanding the Effect of Structural Changes on Slow Magnetic Relaxation in Mononuclear Octahedral Copper(ii) Complexes

“…These initial estimates have indicated suitability of the MSH approach (2). For more accurate calculations of SHPs, we employ the MSH formulas for tetragonal [132][133][134][135][136][137][138] and orthorhombic [139][140][141] symmetry. First, to obtain input data for MSH formulas, the CFPs Bkq [142][143][144] are calculated using SPM for Cu(II) centers in 1 and 2 using the structural data for set C2v (Section IV in SI).…”

“…Please do not adjust margins Please do not adjust margins specific relation was provided for Dq in. [132][133][134][135][136][137][138] However, in the OR case Dq, i.e. E1 in Eq.…”

New Modular Organic Platform for Understanding the Effect of Structural Changes on Slow Magnetic Relaxation in Mononuclear Octahedral Copper(ii) Complexes

“…These initial estimates have indicated suitability of the MSH approach (2). For more accurate calculations of SHPs, we employ the MSH formulas for tetragonal [132][133][134][135][136][137][138] and orthorhombic [139][140][141] symmetry. First, to obtain input data for MSH formulas, the CFPs Bkq [142][143][144] are calculated using SPM for Cu(II) centers in 1 and 2 using the structural data for set C2v (Section IV in SI).…”