Theoretical studies of the defect structures and spin Hamiltonian parameters for manganese(II) and nickel(II) doped Zn(en)₃(NO₃)₂ single crystals

ABSTRACT

The spin Hamiltonian parameters (g factors, hyperfine structure constants and zero-field splittings D and E) and local structures for Mn²⁺ and Ni²⁺ in [Zn(en)₃](NO₃)₂ single crystal are theoretically investigated from the perturbation calculations for trigonally distorted 3d⁵ and trigonally (or orthorhombically) distorted 3d⁸ cluster. The trigonal Mn²⁺ and Ni²⁺ centres are found to undergo the moderate angular variations Δβ of 4.5° and 5.2°, respectively, related to host Zn²⁺ site due to size mismatch. The orthorhombic Ni²⁺ centre shows the relative axial elongation ratio ρ (≈ 2.5%) and the relative perpendicular bond length variation ratio τ (≈0.2%). For Mn²⁺ centre, the contributions to g-shifts Δg_CT (or hyperfine structure constants A_CT and zero-field splitting D_CT) from charge-transfer (CT) mechanism are opposite in sign and five times (or 5% and 8%) in magnitude compared with those from crystal-field (CF) mechanism. For the trigonal Ni²⁺ centre, Δg_CT (or D_CT) are the same (or opposite) in sign and 17% (or 2%) in magnitude related to those from CF mechanism. For the orthorhombic Ni²⁺ centre, Δg_CT and E_CT (or D_CT) are same (or opposite) in sign and 16% and 48% (or 442%) in magnitude with respect to those from the CF mechanism. The signs and magnitudes of the trigonal distortion angles δβ (≈ −0.3 and 0.4°) related to an ideal octahedron and the local angular variations Δβ related to the host bond angle are suitably illustrated by those of the axial distortion degree (ADD) and the angular variation degree (AVD) of the systems, respectively.

KEYWORDS:

• Electron paramagnetic resonance
• defect structures
• Mn²⁺
• Ni²⁺
• [Zn(en)₃](NO₃)₂

Additional information

Funding

This work was financially supported by the Sichuan Province Academic and Technical Leaders Support Fund [grant number Y02028023601041] and the National Natural Science Foundation of China [grant number 11764028].