Theoretical investigations of ESR and optical spectra of crystalline KHSO4:Mn2+

Abstract

Calculations of d-d transitions and the axial zero-field splitting parameter D in crystalline KHSO 4 :Mn 2+ have been undertaken, with consideration of the ninth O 2-ligand. Energy level values calculated in a tetragonal field are in good agreement with experimentally observed values. Occasionally degenerate energy levels of 4 A 1 ( 4 E g (G)) and 4 A 1 ( 4 A 1g (G)) were found in the tetragonal crystal field. The calculated value of D is in good agreement with experimental value for KHSO 4 :Mn 2+ . nine coordinate, tetragonal crystal field, d-d transition, axial zero-field splitting Citation: Xiao X F, Du M L, Miao F, et al. Theoretical investigations of ESR and optical spectra of crystalline KHSO 4 :Mn 2+ . Research on the magneto-optical properties of transition metal ion-doped crystals has received widespread attention [1,2]. ESR (electron spin resonance) and optical spectra are two supplementary tools which can probe site symmetry and associated distortions by crystal structure parameters [2]. ESR can provide information about the magnetic properties of transition mental ions and also symmetry surrounding the mental ion [3]. Optical spectra are useful for studying the electronic structure of transition metal ions in crystals, and can provide information about energy levels and crystal field parameters. ESR of Mn 2+ , a high spin d 5 ion, has been studied in depth, particularly for octahedral and tetrahedral coordinated ions [4,5]. Mn 2+ has been shown to replace K + in crystalline KHSO 4 , with the excess charge being compensated for by nearby K + or H + vacancies [1]. Studies of Mn 2+ in KHSO 4 have been carried out to ascertain whether Mn 2+ enters the KHSO 4 lattice, as has been similarly observed for Cu 2+ [1]. Results can be used to predict distortions, determine orbital level ordering and to probe the interaction between metal ion and ligands [1]. Mn 2+ has five 3d electrons in a ground *Corresponding author (email: xxf666666@163.com) state configuration of 6 S. ESR studies of Mn 2+ have investigated structural and dynamic aspects of crystalline states, because zero-field splitting is sensitive to small distortions [6]. Four, six and eight coordination are most commonly observed in the crystal structures of transition metal ion clusters [7]. Theoretical investigations of ESR and optical spectra are usually based on the above coordination numbers, and d-d transitions of nine coordinate Mn 2+ species have received very little attention. For the case of Mn 2+ doped KHSO 4 , Mn 2+ replaces K + and there are nine O 2-ligands surrounding the central Mn 2+ . One O 2-causes axial crystal field distortions in crystalline KHSO 4 : Mn 2+ [7,8]. The current study investigates the effect of this ninth O 2-ligand on d-d transitions and the axial zero-field splitting of Mn 2+ in crystalline KHSO 4 : Mn 2+ . Crystal structurePotassium hydrogen sulfate has an orthorhombic crystal structure of space group D 2h 15 -P bca . The unit cell dimensions are a = 8. 40, b = 9.79, c = 18.93 Å and Z = 16 [9]. There is